Techcrunch reports that Allen & Co. is raising a venture round for the business networking site LinkedIn at a valuation of $1 billion. The interesting point is that if this did in fact start as an attempt to sell the whole company then Allen & Co, unable to sell the entire company for 1 billion, now wants investors to buy a piece of the company at the same valuation. It begs the question of whether LinkedIn is profitable on their 100 million in revenue because if they were then an IPO would seem to be in the cards. On the other hand, growth in professional adults using social networks is projected as one of the fastest growing segments on the web and LinkedIn is well positioned to benefit from this trend.