Yes this is a rude thing to do. On the other hand are speakers that do not project their voice nor speak into the mike. If you are giving a speech learn how to give a speech! We (the guild) pay up to a thousand dollars for these speakers and pay our dues. If there is a question and answer part - Repeat the question (so everyone hears) and then answer!
Do not mean to hijack this thread but you have HIT ON MY PET PEEVE - SPEAKERS THAT DO NOT SPEAK UP!