I'm sure _most_ Facebook users don't do this, but enough do to make for great hilarity in this particular case. This is all hilarious, but there's no reason to assume it's statistically significant.
Here, for example, is an article from 2007 pointing out that the top search term on Google was... "Yahoo":
http://www.dailydomainer.com/200742-yahoo-top-search-term-on...
Here's Jeremy Zawodny in 2008 musing on the fact that people neither know about nor understand the address bar:
http://jeremy.zawodny.com/blog/archives/010453.html
I could go on like this for a while, but the takeaway is that if you know what your browser's address bar is for and actually type URLs into it, then you're probably in a small minority of web users.