The online registration says the badge is for 3 days, but the show is 4 days. Do I get all 4 days with an online pre-registration?

Absolutely Yes! Yes! Yes!

This is the most frequently asked question.  Here is the most detailed answer to what is going on there.

The company we contracted to handle our online pre-registation (Black-Tie) requires all the details about the registration types, prices, and descriptions up front. 

The company we contracted does not allow the description of the registration item to be changed after being created.

We gave them the information in June of 2009, which was before we extended to the fourth day.  Because we cannot change the description of the registration, we are stuck with the "3 day" badge problem you've seen.