Part of the problem with Myspace, I think, is simple poor design--not a big surprise since, from what I've seen, it's a pain in the butt to configure. I prefer simple, organized sites, but that's possibly my background in tech writing coming through rther than my age (I'm 45). My main problems with difficult web interfaces have to do with my declining vision, I think.

I do think that younger folks may be so used to the idea of always being available--cell phones, IM and so forth--that these things just don't bother them. Personally I don't have a cell phone (they don't work at our house anyway, yay for the country life!) and I don't IM. Sometimes you don't want to be easily accessible, you know?