The world of GunBroker can seem mysterious, but it is well managed. You can't bid on your own auctions unless you have another complete account, different email, different credit card, address, etc. I am not saying there is no monkey business going on but with GB; If you get caught, your gone.
IMHO, GB is far better managed than other auction sites.
One thing you must get used to. Most wait within the last 30 minutes of auction close time to bid. Get used to it. I have seen the 15 minute rule make an auction go on for hours after it supposed to close.
If something is in high demand, you can bet there are other people interested too.
There has been a rash of non paying bidders on GB, quite a few NRs are have been bidding on ammo, which as you know some are paying $1 per round for 5.56 and $10 per box of 22LR. These buyers then catch what is called "Buyers Remorse" This is NOT the fault of the seller as often these auctions start at one penny of more.
These actions cause the NR to be banned and the dealer ends up almost always with a negative feedback. The negative feedback will disappear in a matter of days once the seller reports the non paying bidder.
IMHO I am greatful we have GB as the other auction sites ban firearms and related items.
NR - (No Record) a first time bidder on GB with no feedback.