Something I hadn't fully processed is that many people are using Facebook as an example that real names work. Perhaps this argument is so popular because the Zuckerbergs have publicly emphasized it. At any rate, it's a weak argument. For one thing, quite a number of Facebook profiles are using pseudonyms. See Lady Gaga, Ghostcrawler, and Anne Rice. If the Zuckerbergs really are trying to shut down pseudonyms, they're doing a terrible job of it. Another reason is that, as Boyd points out, Facebook is unusual for starting as a close-knit group of college grads. The membership it grew from is a group of people relatively uninterested in pseudonyms.
Reading the comments to Boyd's post, it appears that the main reasons people are convinced about pseudonyms is the hope that it will improve the level of conversation in a forum. I continue to be mystified by this perspective, but it does appear to be what is driving the most opponents of pseudonyms. I just don't get it. Partially I'm just used to an Internet full of pseudonyms. Partially it's just too easy to think about perfectly legitimate activities that wouldn't be good to pop up if someone does a web search on "Lex Spoon". People interested in that stuff should instead search for Saliacious Leximus. They'll avoid all the nerdy computer talk and get straight to the goods they are looking for.
Overall, pseudonyms appear to be one of those divides where people on each side have a hard time talking over the gulf. Apparently is is perfectly obvious to many people that if Google Plus and Facebook embraced pseudonyms, then their members would get overwhelmed by harassment and spam. Personally, I don't even understand the supposed threat. Why would I circle or friend a complete stranger? If I had, why wouldn't I simply unfriend them?