I totally agree. I can't stand people who put random crap in their Facebook names (and actually tend to unfriend them.)
Similarly, I religiously give everybody on my IM buddy list their real name. I would go crazy if everyday I only saw pseudonyms and had no idea who was who.
What do you do when two people have the same real name? Also, I personally only think remembering everyone's last names, in an area of society where you hardly ever use them, becomes infeasible once you scroll through your address book and find 15-20 people named "Michael" (this is the case in my phone): it is often much more valuable to name people to include their context.
(Which, I might say, is another "myth of names" to add to patio11's list: "the list of names someone goes by is objective and transitive"; I might think of that person as "that Steve from Hacker News", when other people call him "Steve Johanson", "Stevey", or even "stivox".)
I don't use Facebook, but many of my Google+ contacts are people that I've know for years on IRC. I'm going crazy because I can't see pseudonyms, and so I have no idea who's who.
I still don't understand why the fetish for the names from government ID originated. Was it because of Facebook's policy? I'd like to see this trend reversed.
Similarly, I religiously give everybody on my IM buddy list their real name. I would go crazy if everyday I only saw pseudonyms and had no idea who was who.