Digg, which was one of the most popular websites not too long ago, sold for only $500,000. Long story short, they redesigned the user interface and made it uglier and more difficult for anybody to do anything, so people stopped using it. I suppose most hopped over to Reddit, which seems to be a mix of what Usenet used to be and what 4chan unfortunately is.
Also in the news lately is that Firefox has been losing market share to Chrome. This is partly due to Chrome having more efficient internals and partly due to Firefox switching to a stupid versioning system with rapid rabid updates that disable plugins and interrupt user workflow.
The lesson for developers to take from both experiences is to always consider the software from the user's perspective.
[7/13] Clarification : The total value of Digg was $16 million, with the Washington Post paying $12 million to move Digg programmers to Post subsidiary SocialCode and LinkedIn paying $4 million for patents. The $500,000 was for the remaining assets which include the website itself, so it is still accurate to say that the website was sold for that little.