I mean restarting and turning a computer off and on is probably much more "damaging" than closing the lid and reopening it to wake it from sleep.
I am going to say this is perfectly fine to do. It is what the idea of putting your computer to sleep is all about. When you put your MBP to sleep, everything that was in memory stays in memory, so when OS X wakes from sleep, there isn't a lot that is done that would damage your HDD. Nothing is really reloaded and the HDD doesn't spin any differently than it normally would.
But then again, I am not a hardware person =p