>> Perhaps the inhabitants of the Googleplex don't have private lives worth separating, but the researchers compiling Identity Shift don't bring up the issue of how users could present multiple personas online, perhaps because users aren't really doing that yet.<<
Users of bulletin boards, forums (and Wikipedia) have been presenting multiple identities since the days of acoustic couplers. Multiple identities do indeed completely bugger up the best-laid plans to harvest our data.
This is such a serious omission I fail to see how their 'research' is worth reading. Maybe they had decided their conclusions in advance? Which researchers never, ever, do.