There is nothing worse than navigating your mouse to click a link, only to find out the link was actually a dropdown menu. But it's too late, because you already clicked the link, so you're already being taken to a new page.
Example:
The problem? There is no indication this is a dropdown menu. It just looks like a link to a regular page.
So how should it work? If it's a hoverable area, the area shouldn't be clickable because you don't want to take the user to a different page if they click it. I wish more UX designers understood this basic concept. I cannot begin to explain the spout of frustration I just dealt with internally as I just ran into this on Verizon's website.