Polls can be used as a quick and easy way of generating questions for students and language learners to practise their English. A multiple choice question is readily adaptable, and can give you from 1-5 choices. As the poster, you can zip in straight away and post the correct answer. Generally, other native speakers seem to do the same, so the student can depend on finding the right answer after they have clicked, even if they get it wrong.
One advantage of the poll as a question is the ability to have threads running from the question which allow for more than one correct answer or room for doubt. They can also spark off considerable debate; a simple poll about whether it was better to say 'frying pan' or 'skillet' triggered off scores of postings in our old web forum.