Back when @Home folded and Charter had to switch me to their own broadband, I got super pissed because my bandwidth was cut from 4-6mbps actual down to 768k! Same price and everything! So...
I hacked my cable modem. I saw the very first widely published article how the guy described the config replacement hack. I was able to change my speed caps and allow my modem to pull multiple IPs from the network.
Worked great for months until my sister one day loaded up a P2P app and uploaded @ 3mbps for half a day. Oops I got caught, and thought I was in big trouble. Fortunately since it was the very beginning of the whole uncapping fad going mainstream I was able to meet with their network engineer and showed him how I did it. He was satisfied, so they let me keep my account (Charter 768kbps down 128kbps up, what a friggin joke though!)
Now the config files are much more secure, and uncapping is just not doable unless you completely hack your firmware and change your MAC. Even then its still not worth it. I'm happy to pay Charter for my 10mbps, but looking forward to Fios in my area
In no way do I cone hacking the modem. It can't be done these days anyways - at least not with hacks I used. Pay for your service, or if really deperate be happy on your leeched wireless connection