I tried to ignore the term "social graph" when it first started popping up a few weeks ago. For one thing, it sounded like some sort of embarrassing disease; for another, the idea of having to figure out some arcane new Web 2.0 term was depressing. But the term - or is it a meme? - kept on proliferating, so last week I tried to figure out what it meant. The definitions I found, explicit...