Since the screen on a MB or MBP can't be pushed all way down (flat with the desk), I might have to keep the lid closed when I hook up the laptop to my external monitor. The reason has to do with space constraints. So here's my question: Can a Mac be used with the lid closed, or not? I've read warnings from people that say the Macs get so hot that it would damage the machine to keep the lid closed. Is this true, or just an exaggeration? Bottom line: is it okay to use a Mac with the lid closed -- or not? Thanks!