If you also allowed down-voting of a grant, it would ultimately give the masses capability to add or subsequently remove a grant if it was decided it should not be receiving grant coins anymore, as I'm sure would be the case if an individual managed to game that system and vote themselves a personal grant like is currently happening.
This is an interesting idea - but I wonder if it would be possible to structure it in a way that prevents a Mr. Wax style interest fund - where a broad base of coin holders collaborate to split interest payments. Some more discussion on that here -
https://bitcointalk.org/index.php?topic=285232.msg3093133#msg3093133For a multiple grant system - this is the idea I'm leaning towards -
https://bitcointalk.org/index.php?topic=285232.msg3086702#msg3086702