Does running MacBook Pro in clamshell mode cause any damage?

"I have a friend who runs a studio and keeps a Macbook Pro closed and I haven't seen a problem with this.

The only vents are at the back.

However, I can say from my friends one that the heat pretty much evenly spreads out across the chassis."

"I have a 2012 15"" MBP (Non-Retina) that I use in clamshell mode most of the time. I've been doing some video encoding for a project I'm working on and was worried about head since when I'm encoding all processors are running at 100% and the fans are going full blast. I purchased iStat Menus to monitor the temperature and I found that while encoding with the screen fully open and processors running at 100% I was running at a steady 117ºF… while encoding with the screen closed and processors running at 100% I am running at a steady 122ºF. So, yes, it's running a bit warmer but that could probably be attributed to the fact that the GPU is powering a 27"" Thunderbolt Display instead of the built-in 15"" display.

My feeling is basically that Apple has built the clamshell-mode functionality into the machine and I don't think they would have done that if it was going to cause problems. I know that there are a lot of people who run their MBP's in clamshell mode (myself included) and I have yet to meet anyone who had encountered a problem doing this."