Why is that insane? It's inelegant, but it's not functionally different than having an API and a system for registering API keys. Either you trust the aggregator or you don't; if you don't you shouldn't give them access to your data either way. If they do something they shouldn't with your data, they'll be ruined if it becomes public.

(Of course there's a huge gray area of things they could do that you wouldn't like, but that would't ruin them. But there's a clear difference between questionable things, like selling your data to advertisers, and completely not-ok things, like stealing your money).