I've read a few articles recently that warn of the dangers of damaging your camera equipment when taking it from a cold environment into a warm one. The difference in temperature and humidity can cause condensation to form.
I don't see a big problem with the front lens element fogging up but some people have mentioned condensation forming on the inside of a lens and even on the camera sensor itself!
I couldn't find a definitive answer to the question on how important it is to be aware of this issue. Many people seem to suggest that a camera should be sealed in a zip-loc or similar bag and allowed to warm up to room temperature before being removed!
I regularly listen to the excellent Tips from the Top Floor Podcast by Chris Marquardt and decided to send in this question to his show. Click here for a link to the episode and his response.