As you may have heard, AOL has released the search query data for about 500 thousand users. Though the identities were renamed with ID numbers, some people may still be identified from the search queries (at least by those who know them or some detective agency).
Now, of course, the move was probably to generate some link love and popularity that AOL wanted (to be mentioned in the research papers in the universities, of course), but apart from that, AOL has gained the publicity it didn't want.
Here is what went wrong with AOL: