Yeah. I lie every time. At sixteen, I consider myself mature enough to handle most things on the internet--and I'm perfectly capable of choosing for myself what I want and don't want to see. (I'm not into porn.) I shouldn't have to verify my age to check if Blizzard has a release date for D3 yet. By the time it comes out, I'll be old enough to legally purchase it anyway...
Besides, age gates are useless. If anyone really wants to see whatever content is blocked, they just lie anyway. It's such a simple mechanism--if you insert a number high enough or a birth date old enough, it lets you in. I know for a fact that the Diablo 3, Borderlands, and Dawn of War II websites think I am 19, 109, and 79 respectively. It's a waste of time, and in all honesty, developers only do it because they're required to by some moral guardian or another.
I believe Andy Chalk wrote an article about this about a year ago, and I think it was good reading. Any readers of this thread should check it out.