A fragmented identity

Clive Shepherd has put his book collection (or the bits he's prepared to admit to at least!) on a site called Shelfari.

Another interesting niche site, but there are hundreds of these kinds of sites out there these days, all providing a nice way of describing some aspect of your life/work/interests etc. This is an inevitable consequence of capitalist opportunism and entrepreurial behaviour, but do how do you deal with such a fragmented approach to managing our own identity? I heard some venture capitalist on Radio 5Live recently going on about another site for "helping managing your digital identity" - which of course she happened to be an investor in, but that turned out to be another "personal website" space. How do we manage these identities and niche content on a sustainable basis with so many fragmented niche offerings???