I'm wondering how much resellers are really availing themselves of "unlimited" accounts as offered by various (mostly CPanel) providers.

So how many accounts do you currently have on your "unlimited" reseller account. I guess this would count both real commercial accounts plus what you provid your friends/family, etc.

I'm thinking a median point would be around 15. But I could be wrong.

Well it will be a "reasonable" number for a few reasons, unlimited reseller plans are generally limited by the disk space/bandwidth, so it isn't really possible to have "unlimited" domains. Secondly, when hosts surpass the reseller stage they generally move to a dedicated server to cope with the extra demand. So all in all, the accounts on reseller plans should be kept fairly low.

I don't know, there aren't too many votes, but considering that 5 of the 7 votes say 51 (accounts/domains) or more, this is more than I woudl have expected. If you figure 20 reseller accounts on a box (I would guess some have much more), that's 1000+ domains per box. Not too many of these can be real active without consequences for the server.