No; I did think about it for a while since I would've liked to have an excuse for more hash precommitments and whatnot, but I couldn't think of any meaningful way to do it without harming participation.

You can use the Bitcoin blockchain for verifiable randomness, but there's no way to prove I didn't edit or sort the survey results to put a sock puppet account in it. I could release a signed copy of the survey data and commit to a blockchain hash for choice, but then I would have had to release the Bitcoin addresses & emails (because otherwise it's not verifiable in any way), which would damage people's privacy; if I had banned email addresses so as to make it safe to release the full survey data so payments to Bitcoin addresses could be verified, then few people would have been able to benefit from the contest - because as I expected, only like 10% of respondents put in a Bitcoin address rather than an email address. And so on.