This came to my attention via my friend and colleague Sean Christmann (@seanalltogether) from EffectiveUI, who writes:

The next time you're building software and think to yourself, "Don't worry, users will be able to figure it out," I want you to remember this blog post.

ReadWriteWeb recently published an article titled Facebook Wants to Be Your One True Login. Being an interesting, timely article, it rose to the top of Google searches for "Facebook login." Then: chaos and confusion. Lots and lots of the people who use Google instead of their browser's address bar to access sites began confusing the ReadWriteWeb link with a link to Facebook itself, and began posting angry comments wondering why Facebook had been redesigned and asking when they'd be allowed to log in again. RRW posted a fascinating response to this bizarre event wherein they attribute the failure to Google, and note the disturbing security implications… makes for very interesting reading.

But definitely set aside some time to read some of the comments thread on the original article. It's really eye-opening. And if you haven't already seen it, check out this video of a Google rep asking random people, "What's a browser?" and "What's the difference between Google and a browser?" I'm betting the people who got those answers wrong are the same sorts of people who flamed the RWW post.

Remember these people when you're designing your products.