I found this great post from the founder of Dropbox, Drew Houston, on Hacker News.

Someone had asked him if Dropbox (currently valued at $5b) was his first idea.

“[I] informally came up with and tossed around 6 or 7 ideas at the same time — not so much coding as investigating/talking to potential customers and bouncing them off other friends and entrepreneurs.

this was crucial — ideas don’t really fall out of the sky, they evolve.

there were several times where i’d get really excited…