Sometimes the problems with angles is over doing it. It's good to take an angle when the picture warrants it, like when the subject is on a hill or maybe when you are trying to give something an upward view to kind of stretch the picture or maybe when you are trying to include something in the background.

Personally, the problem comes in when people try to emulate what they see on the cover of a magazine X 10. If you notice on the mags, the background plays a big role in the picture as a whole. Most people see those covers and see the angles and try to duplicate them w/o taking the background into consideration. If you have a blurred background, extreme angles work. It also works when you have the sky as the main background. When it doesn't is when you have a busy background which lets you see just how extreme the angle is.