Online coupon company Groupon filed for an initial public offering of up to $750 million, the latest in a series of Internet companies to tap the U.S. capital markets. In April, a source told Reuters that Groupon could raise as much as $1 billion in the IPO, which could value the fast-growing daily deals site at $15 billion to $20 billion. The IPO filing did not specify the number of shares to be sold in the IPO, the price range, or the exchange, though it did say the shares would trade under the symbol “GRPN.”

Groupon is losing an astounding amount of money, but generating an equally impressive amount of revenue, writes Silicon Alley Insider’s Jay Yarrow. In the first three months of 2011, it had a net loss of $114 million. For all of 2010, its loss was $414 million. For the first three months this year it generated $645 million in revenue, a 1,366 percent increase from the year prior, when it generated $44 million, adds Yarrow.

The hacker group calling itself Lulz Security said that it broke into servers that run the SonyPictures.com website, and then compromised the personal information of more than 1 million Sony customers. Lulz Security said in a statement posted on its website that it hacked into a database that included unencrypted passwords as well as names, address and birth dates of Sony’s customers.

Washington scrambled to assess whether security had been compromised after Google revealed a major hacker attack targeting U.S. officials that the Internet giant pegged to China. Neither Google nor the U.S. government has said the Chinese government was behind the attacks. Beijing nevertheless reacted angrily to Google’s charge, saying it was “unacceptable” to blame Beijing and allegations that China supports hacking were unfounded “and have ulterior motives”.

The Executive Office of the President, which includes the White House and related offices, blocks access to outside email services such as Gmail, Hotmail and Yahoo Mail on its networks within the complex. Other agencies also have firewalls to block access.