Yeah, I've got a guy that 3-4 times a day, marks a cop, object in road, vehicle on the side of the road, and a traffic jam in front of his house. He does it in the morning, before and after lunch, and then when he gets home.
I've commented a few times, telling him to stop reporting non-existant items, but it does no good. Not much can be done about this.
I 2-3 nights a week, 14-16 hours to edit. We work to editors around 100 steps, and save. Save do not look forward to doing again in a another window of about 100 construction. And so it turns doing it. So I can do it for a week around 20,000 points.
I suppose it depends on what you mean by cheat. I see user tracks all the time which have clearly been generated while sitting on a train. I see users report minor potholes etc (one regular user leaves a little trail behind them all the time.) there used to be users who would ping many times (fortunately that no longer gets points). As for editing I can see a large number of ways of cheating - marking URs fixed when not, repeatedly making unnecessary changes, etc. At the end of the day we have to rely on trust.