I was just listening to this talk by Steven Johnson about "Where Good Ideas Come From" and it conveyed some really important message. People who are thinking "Oh I never have a good idea" and thinking when will the eureka moment happen are not in vain. "An idea is a network of neurons" that was never formed before. It takes months and even years for an idea to incubate before it finally transpires through the "Eureka moment". For example, Darwin had his idea of natural selection incubating and had all his smallest hunches about the theory written down in his diary .. until one final day they strike in his epiphany.
Another interesting point was that good ideas occur during interactions - in coffee shops, in meetings - while discussing errors, interesting wonderments, etc. An idea is not independent but it is interlinked with the surroundings - a story from someone, an incident, an accident.
Bottomline - good ideas develop with conversations, although the Eureka moment may occur at some other point of time.
P.S. Coffee shops are great idea incubating places! :D