By Kevin Kelleher
The opinions expressed are his own.

Failure is a funny thing in the tech world. An entrepreneur can get fired from a company he founded and his peers will watch to see what he does with the lesson. A young company can burn its cash like a Viking setting his ship on fire, but be remembered wistfully once it’s bankrupt. For startups, failure sometimes seems like a rite of passage – the painful second act of a three-act story with a happy ending.

But it’s different when a big company stumbles, losing its place at the top of the heap. Nobody cheers you on. You just seem like a stock character in someone else’s legend – the hoary old giant descending so that another can ascend. For big tech companies, failure is the grim final act that can stretch on for years and years. Until no one wants to watch anymore.

In the annals of tech brands that have risen and fallen – DEC and Wang in early computing, Sony in consumer electronics, AOL and Yahoo in the Internet – the declines have taken several years, at least. But few tech giants have fallen as quickly, or as dramatically, as Research in Motion.

By some measures, Research in Motion still appears healthy. Its Blackberry smartphones have 70 million subscribers around the world, and it’s far from losing money – analysts expect the company to post revenue of $19 billion and a per-share profit of $4.13 this year. But they also expect profit to fall 50% this year (even after 2000 layoffs since July) and another 30% next year. The key reason: Blackberries are quickly losing market share, which fell to 16.6% from 19.7% between August and November.

The severity of the decline is clearer in RIM’s stock, which ended 2011 near a seven-year low, having fallen more than 90% in the last two and a half years. In 2011 alone, RIM has lost $27 billion in market value – more than Nokia is worth and more than twice as much as Google is paying for Motorola Mobility.