Restart hurts a mac? I always thought it was a good thing to restart (at lesast in windows).
A restart isn't any more damaging than force-quitting a stuck application (in other words: almost never is it truly harmful). What CAN be troublesome is forcing a Mac to shut down by holding down the power button for several seconds. That gives the Mac no opportunity to gracefully finish any pending changes or writes to the hard drive.
This is equally true in the Windows environment though. And even then, it's still usually not the end of the world, in either case. It's risky, but not universally bad.
Even so, there's still less of a reason to restart a Mac when you can just force quit the offending process, and either relaunch the app, or let the process re-spawn on its own.
The "when in doubt, restart" mentality comes from the chronic Windows problem where it (and programs running on it) lose track of memory that is no longer being used. This is called a
memory leak. Back in the Windows 95/98 days, it was so bad that just booting a computer up and letting it sit without running any programs would still cause it go more and more unstable until it crashed, all on its own. The only way to get aroudn this problem was to restart often.
Windows XP isn't nearly as bad, but some badly coded programs can still cause issues, so restarting from time to time is still viewed as good advice. And Vista is just a resource hog in general; no amount of rebooting will cure that. But people will still try it anyway.
As for OS X: its memory management is pretty good and so memory leaks aren't nearly the problem they've been on the PC side. Some programs (Adobe applications, Safari, Firefox 2) do hog more and more memory the longer you keep them running, but that's easily solved by restarting the application, not the whole system.