You have always been able to buy your own cable modem from Mediacom (my service provider). Back in my IT days I was looking into buying a Cisco cable modem but then I thought more about it and realized, I am paying 6 bucks a month extra to rent a modem that would cost me 100-200 dollars on Ebay. I used to burn threw modems like crazy just never made sense. Renting sometimes works in our favor too.
My cable box sits on top of my stack of equipment, its the heat absorber = ).