submit your idea and vote for your favourites

This, this and this all collided in my head the other day. On the one hand: as a charity with limited budgets and (if you're good) a well defined strategy for achieving what you want to do, you might not want to listen to other people's ideas about what you should be doing. On the other: why hasn't a charity found the right level of (or at least started toying with) crowdsourcing ideas to do good?