LJ trivia: why can you see poll results even if the poll is visible to "none"?
Answer: you can see the aggregate statistics (percentages and bar graphs), but you can't see individual data (i.e. who voted for what option). This is even documented in the FAQ, though I had to look a bit and found it mostly because I knew where it would have to be if it were there, not because it's particularly prominent.
This came up in the context of a support request I submitted a screened answer to.