Truth is, you can't really manage your digital identity ... at least not all of it. It's not entirely up to you, nor has it ever been. But you can get a whole lot smarter about all the info about you that exists on the Web. Bruno Giusanni points to Fred Cavazza's "framework for mapping our digital identity (or, rather, identities)." He notes:
increasingly, footprints appear on the digital sands over which we don't exercise any control: people blog about you, take and publish pictures, and if someone searches for your name in Google or GoogleBlogsearch or Clusty or IceRocket or Technorati, up comes whatever comes, and that's also defining your digital identity - each one of those search results composes one of your digital personas, giving information and hints about what you do, your character, your opinions, your network, in short, who you are. And there are more: just think of Second Life avatars.
And this is what exists in the visible world. Much more is known about the people who inhabit the Web, and the debates regarding anonymity and privacy will continue (a persistent concern of mine). In the meantime, understand your own footprints as you work and play and understand what you -- the guy or gal who has just been annointed Time Magazine's Person of the Year -- are contributing.