Uhm, anyone with an ISP in the United States is going to have a block delegated from ARIN. That's the whole point of ARIN, isn't it? Nothing they delegate is inherently special, because ARIN administers all of the allocations for their region.

I'm saying that perhaps the 2600::/16 delegation is especially reserved for a certain class of user in order to tag us as something. Surely, my own ISP holds more delegations than that slice alone. It's certainly standing out like a sore thumb to anyone analyzing logs. As I said, it can't be merely a coincidence.

Interestingly, I also subscribe to mobile voice/data service from the same ISP, and activating mobile data here at home gives me, sure enough, another 2600::* delegation.