Here's one[0] about when Facebook changed something about their login, and someone wrote a blog post about it. The blog post ended up being top Google result for "facebook login". A lot of people, it seems, were getting to facebook not by the address bar, but by typing "facebook login" into Google, and clicking whatever the first result was. Hence, they found the site, then proceeded to leave tons of comments, complaining that they couldn't log in to FB.
[0] https://web.archive.org/web/20120201181225/http://www.readwr...
EDIT: This was similar to what happened to rapgenius a bit back. Google blacklisted their site, and people thought the site was deleted, and were complaining to rapgenius on twitter. It blows my mind that there are a lot of people that don't know how to use an address bar properly.