AOL

In 2006, AOL got in trouble for publicly releasing  keywords that 650,000 users from their website had used. These keywords were available over  a three month period. This was suppose to be for research purposes, however this made it possible to identify specific users and what their search history was. AOL eventually recognized their mistake and took down the keywords.  Unfortunately the keywords had been mirrored all over the internet at this point and it was much too late to do anythign. AOL got sued by a class action lawsuit for the tune $5,000 per user or a cool 3.25 billion dollars. This lawsuit is still not settled, an is working its way through California courts. heres an article from 2006 about the search leak http://news.cnet.com/2100-1030_3-6103098.html