@Mark @reurbo What's the point of someone being banned if the can come back and make a new account? It seems like a loophole of being banned. Then why even ban them in the first place. If they are able to come back to the site.
It's the same for any website. You ban by the usual things such as IP address and email and sometimes you expand that to a range of IPs or entire providers (e.g. VPN services), if collateral damage is acceptable.
Anyone can ultimately get past any website's ban if they have the determination. So a ban essentially acts as a deterrent and it is generally quite effective at that.
The flaw in the system at CC is currently deleting your account totally destroys it instantly. But very soon we will keep deleted accounts for 30 days which will help stop those that jump in and out in order to try and avoid leaving a footprint.