There is nothing "special" about Web 2.0, other than you likely need something with a decent database option.
I'd look at something like Slicehost, or more of a hosted server vs. shared server solution. Skip EC2 for now, and other things that are a little too progressive. You need (IMO) a solid stable base first, then look into elasticity when you get some mass.
If you want/need a dedicated server, send me an email I can get you setup with something nice.
