I rarely use mine. Except in instances where people post like an ass, or if something is screaming spam. I think I've only flagged about four or five things, in total.
About 20-30 times daily, but only on people who say one or two word responses for no reason, such as "okay" or "not bad" about a game. However, if someone comments something like "too hard, but cool" it's fine. i just hate people who spam all the time, as it is effectively cheating.
Every time I comment on a game and realize how many people have left spam comments. Latest examples I bumped into are 'gay', 'afgdrahgadttthhhjkkkj', 'nice', 'cool', 'boring', 'bad', etc... Also those who just post a rating, as it really is spam according to the guidelines. Comments on games should at the very least state WHY people like/disllike the game. I don't use it elsewhere. Might if I see flamers.