Almost sounds like gaming the system when they do that (particularly for the benefits Reece lists), and it can get mighty annoying when you have to go through the trouble of bidding a certain amount (not just $60) only to get an email about a counter-offer that is 100,000% more than what you bid. It'd be better if there was some guidance as to what their expectations so that it doesn't waste peoples' time.
But then again it's totally legit, so you can't really blame them for taking advantage of it.