Yesterday, I read a really good article about the negative impacts of hover menus at uxmovement.com. In it, the author brings up some good points about how hover menus (also called pulldown or rollover menus) can negatively impact the user experience on your web site.
He did a great job of explaining the pitfalls of hover menus. I'd like to add a couple more and then talk about reasons why clients ask for hover menus in the first place.