I had an idea for polls / vote. It would be something like the vote is a dm to a pubkey, that pubkey compiles the results from all the dms. you can verify that a pubkey voted, but not what the vote was...
Discussion
I guess votes being public for a start is ok. It just should be made clear to the user that that's the case. Also I doubt clients will force users to vote to see results ... or that there is some fancy, non-interactive crypto that could enforce that.