Maybe you can't find people from real life with pseudonyms, but not all of us have that problem. Where I'm from -- literally, my geographic area -- social networking under nyms is so normal, that if I want to find someone on the internet, I say, for example, "Hey, are you on LJ? I'm so-and-so on LJ." And if they want to have anything to do with me, they can come "friend" me there. I have almost 300 people on my LJ flist, about two thirds of whom are people in my f2f social circle, the vast majority of whom I've worked with as a musician.
No, the pseudonym-finds-pseudonym thing only breaks if you can't or won't ask someone what their nym is. In other words, it prevents you from finding people who don't want to be found, and who you have no in-person contact with. Sounds like a feature to me!