How many sites can wordpress multisite support on a single VPS?

OK, so I know this is a "how long is a piece of string" type question, and i know it is dependent on the hardware that wordpress is running and the amount of traffic that each site is getting.

I was wondering if members that are running small to medium sized installations would be able to share some basic stats such as the hardware that they are running on, the number of sites they are running and how much traffic they get.

Thanks,
Joe