Do I need a 1.1 2.0 or 3.0 USB port?

I'm looking into buying a UBS hub and I have seen some with 3.0 ports while the less expensive ones are marked as compatible with devices that require 1.1 and 2.0 ports, now I'm fairly certain that at least some of the USB ports on my computer are 3.0 (I remember seeing it in the specifications when I bought the computer and wondering then if that was something I really needed, until then I hadn't realized that there were different types of USB ports) so what I want to know is...

1. How likely it is that I'll run into problems if I buy one of the cheaper hubs that only have 2.0 ports

2. What sorts of thing would require a 3.0 port &

3. If I shell out for a hub with 3.0 ports and use an extension cable is there anything I should watch out for there.

Also unless I can find a hub with a fairly long cord I'll have-to use an extension cable with any hub that I get and I'm typically going to be using it for things such as a web-cam, thumb-drives, my phone, and maybe my wireless gaming headset when it needs to be charged, so the web-cam is probably the big thing and it's what I'm buying the hub/extension cable for.