Using polling questions during a webcast presentation need to be timed correctly. You need to carefully explain that you will do a polling question and what the actual question is. You will have to ask the question more than one time to ensure that everyone of your audience has heard and understood the question and can participate.
Besides asking the question the polling question should also be visible on the screen so your audience members can also read the question. Next you need to provide sufficient time to answer the question. This may be a delicate balance as there needs to be sufficient time to answer the question, but also not too much so it will leave your audience time to disconnect and get distracted by something else.
Having too much time for the polling question can take the flow out of your webcast presentation, therefore you have to be careful with that. Some webcast software shows a count down timer on the screen with the polling question. This could be helpful for your audience to keep track.