Opening our RealTime CrunchUp event today in San Francisco is Twitter COO Dick Costolo . Our own Michael Arrington and Steve Gillmor are sitting down with Costolo for a 30 minute conversation. Twitter is one of the hottest players in the realtime field right now. And it has a $1 billion valuation , which has been the source of much controversy. Twitter also recently signed search deals with both Microsoft and Google . Below find my live notes (paraphrased):