With nearly 400 million users, Facebook is increasingly challenging the traditional Web overlords like Google and Yahoo on all fronts.

So the reports on Friday that Facebook was developing its own Web-based email, supposedly referred to internally as a “Gmail killer” raised a lot of eyebrows – not the least because Paul Buchheit, the former Google engineer who created Gmail, now works at Facebook (Facebook acquired Bucheit’s social networking startup FriendFeed last year).

But if there’s a Facebook email product in the works, Buchheit isn’t working on it.

In a post on to his FriendFeed account on Friday, Buchheit said, “No, I am not working on anything related to email,” adding that he did not plan to either.

Apple has a reputation for developing hit products.

But the company also has a rep for maintaining an iron grip on its image and its message. Wednesday’s launch of the iPad, a product whose details have been closely guarded by Apple for months ahead of the launch, showed Apple’s operation at its best.

To the surprise of many, Apple CEO Steve Jobs turned up at the demo room after the main event and appeared to be casually hobnobbing with Wall Street Journal tech columnist Walt Mossberg.

But the scene was hardly the impromptu, open conversation it appeared.

With Wednesday’s expected unveiling of the Apple tablet, the tech world is bracing for a device that could revolutionize everything from mobile computing to the newspaper industry. But what if the tablet doesn’t live up to expectations?

While Apple is known for its golden touch, the company has had its share of flops. The five products below represent some of Apple’s biggest disappointments; but they also provide important lessons that can be found in its smash hits.

Newton: First released in 1993, the Newton represented one of the first attempts at a mass-market, touchscreen-based handheld computer. But the brick-sized Message Pad family of devices that ran the Newton operating system were too big and, at $700-plus, too pricey. And the mixed results of the initial version of the handwriting recognition made Newtons an easy target for criticism.

While some cite the Newton as a progenitor to the iPhone and the expected tablet, it’s notable that the Newton was developed while Apple CEO Steve Jobs was in exile. Within two years of Jobs’ return in 1996, the Newton was cast overboard.

The last time the world had a look at Twitter’s financial books, the company was targeting a meager $400,000 in revenue for the third quarter of 2009 and $4 million in the fourth quarter.

But that information was based on documents stolen from Twitter by a hacker and republished by the blog TechCrunch.

And it was before Twitter, the popular microblogging service that allows users to broadcast short, 140-character text messages across the Internet, had inked monumental deals with search giants Google and Microsoft.

The companies have kept mum about the financial terms of the deals, which will allow Tweets to appear in Google and Microsoft’s search results. But people familiar with the situation have told Reuters that money did change hands as a result of the deals and the blog AllThingsDigital previously reported that the search deals could be worth several million dollars apiece.

The grousing about Facebook’s recent privacy changes is now an official complaint.

The Electronic Privacy Information Center, along with eight other groups, filed a complaint with the U.S. Federal Trade Commission on Thursday urging the regulator to open an investigation into Facebook’s new privacy settings.

Facebook’s privacy changes “violate user expectations, diminish user privacy and contradict Facebook’s own representations,” reads the 29-page complaint, which accuses the world’s No.1 Internet social networking company of engaging in unfair and deceptive practices.

The complaint comes a week after Facebook unveiled sweeping new privacy changes that it said were designed to simplify privacy settings for its 350 million users, and to give users more control over who sees their personal information.

Everybody knows social media firms are growing like gangbusters. Facebook, for instance, recently surpassed 350 million users, 16 months after reaching 100 million users.

How much money the Web start-ups are making is less clear — though industry-watchers were treated to a few tantalizing revelations this week.

Facebook is within striking distance of a $1 billion annual revenue run rate, according to TBI Research analyst Rory Maher.

That would be a dramatic increase from the $500 million in 2009 revenue that Facebook board member Mark Andreessen touted back in July.

If you’re an Internet search engine, having Twitter content adorning your results has become as fashionable as claiming a Tiger Woods liaison seems to be for a certain group of people.

Google and Microsoft both raced to announce deals to incorporate Twitter in their search results within hours of each other in October.

And Yahoo – despite its plan to cease investing in back-end search technology and to outsource the job to Microsoft – does not want to be left out of the action.

Yahoo announced that it will display Tweets – the pithy 140-character messages continuously churned out and broadcast over the Internet by Twitter users – in a larger portion of its search results.

Celebrity deaths are big news. But nothing warms a media executive’s heart more than a good celebrity sex scandal.

“God bless Tiger. This week we got a huge uplift.” Yahoo CEO Carol Bartz told a crowd of investors in New York on Tuesday at the UBS Media and Communications Conference.

Reuters

Bartz noted that the Tiger Woods story has filtered through all of Yahoo’s key online properties, from front page news to websites dedicated to sports and gossip.

The doors of restaurants and barbershops are increasingly plastered with stickers touting various online rating services, from Yelp and Citysearch to the distinctive red crest of Zagat.

Now Google wants some of that door-panel real estate.

The Internet search giant is mailing out special decals to more than 100,000 small businesses across the U.S. which have been identified as Google Favorite Places.

The stickers feature a special bar code. Snap a photo of the bar code with your smartphone camera (such as an iPhone or Google’s own Android-based phones) and you’re automatically served-up reviews and other information about the particular merchant.

Unlike many of us, media executives know what it’s like to play around with large wads of cash. So it seemed natural to ask them about what kind of investment opportunities they’re seeing when they gathered in New York this week for the Reuters Global Media Summit.We gave each media honcho $10 million in hypothetical cash and told them to put the money to work without buying stock in their own companies.Some executives plowed the money into broad sectors and regions, like emerging markets, while others zeroed in on specific stocks, like Electronic Arts’ CEO John Riccitiello’s penchant for software maker Adobe.Zynga CEO Mark Pincus said he already owns shares of privately-held Facebook, the Internet social network on which many of Zynga’s video games are designed to be played on, and that he’d buy more on the secondary markets (OK, so he creatively sidestepped the rule against investing in his own company).And some media moguls seemed to have investment strategies driven by goals other than maximizing returns:”I would put it in US-based international equities. I mean, if you said….If you forced me to invest a dollar.”(Reuters: You can put it in your pillow if you want.) That’s what I’ve been doing. Unfortunately, the pillow was unsleepable-Barry Diller, CEO, IAC/InterActive Corp”Pay off my mortgage in Nantucket. That’s probably the safe answer with my wife.”- Mark Greenberg, CEO, Epix”Leeds United (British soccer club) — I’ve seen them recently and they could do with the money.”-John Ridding, CEO Financial Times”I think having a good time, for the next five or six years.”-Mitch Lowe, President, RedboxSee what tech and media executives said in May 2009, December 2008 and May 2008.