The glass used by Canon for the screen is so astonishingly tough, the only people who would say you need protection are the manufacturers of the protection.
I shoot every day with two-three bodies and have done so with digital for all of this century. I smashed a screen on a 1Ds when it flopped back on a tripod that wasn't locked. Canon CPS fixed it for free in 10 minutes. I very slightly damaged a screen on a D30 (not to be confused with the 2006 30D) after it bashed continuously against a belt buckle while attempting to ride a horse. I'm not especially careful with my gear, and other than those two careless mishaps every screen I've had has been pristine at the end of 2-3 years of hard labour when the bodies are upgraded.
Save your protection for other fun pursuits.