There's plenty of online polls around today and most of them require your email address before you participate. But do they really need your personal email address? Not really.
In order to conduct a poll, the poll takers only need your answer. They don't need your name, they don't need to know where you live and they definitely don't need your email address. So why is it that so many sites online request your email? There's multiple reasons. They could want your email so they can market to you (i.e. try to sell you stuff) by emailing you offers. They could be building an email list of people and then selling that email list to marketers and spammers. Both of these are not good enough reasons, unless you truly are interested in the products and services they are trying to sell you.
A possible more legit reason is that they want to make sure that they only receive 1 vote for the poll per email address. Unfortunately this is a very ineffective way of enforcing protection on an online poll. Many people already have a work and personal email address, so already they could use both of those for 2 votes. PRO TIP: Do not use your personal email or work email, use a temporary email, like one you would get from EmailOnDeck.
Websites can enforce 1 vote per person polls by doing IP restrictions, and browser fingerprinting. There are other techniques too. So don't let anyone convince you that your email address is the sole way of ensuring poll integrity. Protect your privacy and use a temporary email address for online polls!