When you should NOT use a poll?  For that matter, when should you avoid interactivity of any type?

When it’s fake.  When it’s interactivity or the sake of thinking you should be interactive.

A good place to start is by first considering what you would do if you were in person.  Would you talk to the audience, never answer a question, never ask them to raise their hand, never ask them to comment on what you just said?  That’s a bit extreme except for keynote speeches, but most web seminars/webinars/webcasts in today’s world are to educate or persuade.

And if you want to optimize how well your audience remembers, if not acts upon, your messages, your best course of action is to think about how to engage them.  So…where would you?  Introductions at the beginning?  A raise of hands asking “how many of you are here from the healthcare industry today?”

You get the idea.  Despite some folks telling you to be sure to insert a poll every 4-6 minutes or have the obligatory Q&A session at the end, your best bet is to figure out how you’d naturally communicate with your audience and then adapt that to the online medium.  To be sure, many presenters would do well to get more interactive, but forcing it accomplishes nothing, and likely also wastes everyone’s time.

Don’t use a poll to use a poll.  Be natural, and learn the tools of the virtual presenter so you can be as natural online as off.