[DougWebb]

As far as I'm concerned anything that sits on a port waiting for a connection is a "server" and its almost impossible to do much online these days without unknowingly running one.

Absolutely true. I'm on Comcast too, and technically both my Tivo and WiFi router are 'servers' because they accept incoming connections from the internet. I also run a regular server for a few things, and I've never had a problem, but it's all been for personal use and light-bandwidth. I think if I started streaming multimedia out of the house, I'd run the risk of setting off some bandwidth usage flags. But so long as your total in+out bandwidth is within their cap (250GB/month on my residential service) there's probably no problem.