A PhD can NEVER be a entrepreneur. He/She is too straightjacketed brainy fellow who knows the BEST solution to a specific problem.
A PhD in Computer Science may be a wing of CS (Encryption, Chip Design, etc) in which she is a king. Take them out of the area and put them... let's say work on configuring W2K for a proxy Server and they will fail miserably.
PhD do NOT have presence of mind and adaptability and would never fit into a take-risk venture.
If google wants to venture out of search business into other arenas, it needs to hire more jack-of-all trades guys and not PhDs.
BTW, i did not rant against PhD, George Soros words were the ones i quoted above.