There aren't enough available v4 IP addresses available to Amazon to assign a different one to every 3G Kindle. I'm not sure how a 3G connection gets mapped to an IP address, anyway, since it is not the usual way of connecting to the web (cellular, as opposed to wi-fi/normal hard-wired network connection). The older Kindles only had 3G, and they sold a ton of them.
I googled this, and I don't see anything about editing of wikipedia being blocked from Kindle. Did you get an error message while trying to edit a wikipedia entry? It is quite possible that the wikipedia editing screens are too much for the Kindle browser to handle.