While Kemmlerian necromancy doesn't have a sponsor per se, meaning that there's no big entity deciding who gets to use it, and how, it does have an agenda. It's an ideal, all about self aggrandizement through the practice of necromancy (or whatever interpretation you and your GM prefer, but I like mine). Since the GM is always the sponsor anyway going into sponsor debt just means that the GM can then force you to ask "What Would Kemmler Do" some time down the road.
Similarly, we've heard about the Merlin throwing around wards in a very evothaum sort of way, to the point where "Sponsored Magic: Unyielding Defense" could be an option for someone trained like him. In his case sponsor debt would cause him to make the Council engage in purely defensive warfare with an aggressive enemy, be highly suspicious of any new or untested allies, or cut off staunch supporters rather than take a risk in defending them. (To be fair,
Peabody's ink might have done that as well
.