We might see a lot of more well-funded start ups begin jumping into the Bitcoin space soon. The incentives increase with the market cap.
Naval @3:10, says ~$3-5B market cap range:
http://www.youtube.com/watch?v=Jl-HZWfxUFw
We're sitting over $4B at Stamp rates now. Passed $3B a while ago as well (sat around ~$2B for quite a while).