LinkedIn shares have done really very well since their IPO, but they could of course be a proxy for the debut Facebook IPO which floats today. Will the fizz come off LinkedIn shares as investors realize we may only have the time for one social network? Or could it be that multiple social networks are the way forward? Could FB compete with the work and career oriented social network of LinkedIn.com? There is already the company Branchout which aims to be the LinkedIn career network inside Facebook.