Here's a scenario. If say a user is logged in and is using one of those wireless 3G USB sticks out in, let's say, a park or whatever. Are they likely to get logged out of their session if their coverage is either disrupted, or their coverage roams/moves to another cell mast? This also could extend to mobile devices on 3G/EDGE or similar, even in their own home if their router packs up and they've jumped to a non-WiFi connection protocol. That's about as in-depth as I can explain it. So, what's the deal with sessions/IP?