3 and 5, i really doubt people will pay taxes
The moment I cash out Bitcoins I will pay taxes, just like I would pay taxes if I was selling WoW gold. It's an income, and that's something I pay taxes for. It's simply the way people currently do business - just like when you purchase and sell other commodities or services for profit. If I wanted to avoid paying taxes, I'd have to go the long route of creating an off-shore company and off-shore accounts and make sure that I'm not officially the owner ... and have to be super-careful that I don't run into one of the many pitfalls along that path.
Bitcoins wouldn't really help me much with that (anything I could do with Bitcoins, I could also do with an offshore-account - same risks, same benefits).