I don't actually act like this when I DM, but I could. I do openly attempt to manipulate people by giving and removing horse points. They don't do anything, and it's no secret. But I've seen people trading horse points to win minor arguments, or bragging that they have more horse points.
They're a sort of ethereal wisp of a currency, but they're still a currency inside of my group, and I think that's wonderful.
(I may or may not actually own a cloak that looks like that)