Hivelocity, do you mean "sponsorship" requests in general or game server request in particular?
It would seem strange to me that someone would bother you, a business, for such free requests every day, unless: (a) they know you personally; (b) you offered free hosting somewhere previously.
I think that every hosting company should decide what kind of venture they want to run, how profitable, and if sponsorship hosting could eventually pay off. If you are positive that these guys can bring you more business that it would cost you to host them, then go with it. However, if unsure, then your reply "pay for play" is the right one.
Simple accounting law: accept decision if its VALUE exceed COST. I'm not a host, so its hard for me to understand the cost of running a game server per se, but you do the math.
Best,