Proxy oder was?
 

Here's where my complete lack of knowledge about this business reveals itself once again. ;)

What is going on when a submitter's IP matches that of his host? I assume he or she is either using some type of proxy or has submission software installed on his or her server. Am I warm? I've seen this a few times in the past, and I used to instantly black list for anything I didn't understand, but I have a new submitter doing this, whatever this is, so I'm wondering how leery I should be about the situation.

Uw,

It could be a few different things. Having a proxy is probably the most likely. But it might also be a VPN or some sort of submission software as well. Or, in all honesty, they could be using it to hide that they are multi-submitting or that you banned them at their old ISP, etc.

A lot of people use proxies like that as it can establish a more secured connection that is harder to eavesdrop on. I used to use something called SSH (secure shell) forwarding to do this so that my (old) ISP basically did not see which sites I frequented and my personal business. Everything between my server and the ISP was encrypted.

I am anything but a hosting geek, but isn't it possible that the host's website and the submitter's website just share the same server/machine and thus share an IP address?

If the submitter's host was a tiny reseller, or if the host was a front for a group of folks using the same dedicated server, sure, but that's not what I'm talking about. ;) I mean the IP of the submitter him/herself - which should be from their ISP and not having anything to do with where their sites are hosted.

Got it ;) I thought you were talking about the IP address of the site/domain.

Maybe he is his own isp and using a local machine. :D I really don't know other than what you already suggested and my little guess..