Yes, of course some people try to take things too far and go totally over the top.
When you run your humidifier too much, the air becomes saturated. It can only hold so much moisture. If you continue to try and pump more into it, you will start getting condensation.
You will first notice this on cold surfaces like windows, and the surface the machine is standing on may become damp.
The main factor that determines how much moisture the air can hold is it's temperature. As air comes into contact with a cold surface like a window, its temperature falls, so the amount of moisture it can hold is reduced. This is why you get condensation.
If you have some particularly cold surfaces in the room you will be fighting a losing battle, as they will be causing condensation and reducing the humidity as quickly as you can raise it. The only solution is to fix the source of cold that is causing the problem.
For those who aren't in this situation, it is still possible to go over the top, so keep an eye on the situation and make adjustments when needed. This can be done automatically if you buy a model that has a built in hygrometer which measures the humidity of the air. There are some models in the reviews section that do this particularly well.