forum members with multiple IP's

[dadoc]

I was wanting to get some advice on forum members with multiple IP's,

On my site there is a rule that you can't have multiple accounts and that you can not share your account with others.

We have been keeping an eye on some of our members and we have the issue of a member logging in with multiple IP's.

We have asked this member why this is the case and the reply we get is that he likes to be anonymous when he is online.

He has logged on with IP's from all around the world.

He has not given us a reason why this is and we are looking into whether we should ban him or tell him that he can only log into the site with the IP that he registered with. I know that members will always now and then log on with a different IP as they might just be logging in on another computer and there is no problem with this.

Is it something that we should be concerned about ?

Do you have a rule on you forum that bans proxy IP's?

What is the answer to this?