I have three personas: my professional, my personal and my social. Some people see more than one of my personas depending on context - if I'm out with a bunch of friends and run into a VC, I quickly switch into my professional persona.

Separate websites for each social context makes my life easier. LinkedIn is professional. Facebook is social (well, before my contacts got mixed up). Dating websites are personal.

Google+ doesn't provide a strong visual indicator to help me switch contexts. I'm not absolutely certain that I haven't mixed up one of my business contacts with my personal ones. Add to that the chance that something gets sent out publicly by mistake and there is absolutely no chance I'll use G+ for anything beyond Twitter with pictures.