Yesterday LNKD closed trading at $8.9 Billion in market cap. In 2010 they made $280 Million in revenue and $4 million in net profits. In 2011 they project $400 million revenue and $10 million in net profits.
I like their service and product, it is a legitimate business. I've been to their campus a few times and liked the culture/work environment there. But from an investment standpoint it is extremely overvalued (to put it lightly) and there will need to be huge growth to simply catch up to it's current valuation.