Higher registration numbers is good for Network Solutions, Godaddy, etc. But higher registration numbers doesn't necessarily translate into higher sales.
I haven't seen too many threads about .biz sales. That's probably because you're not supposed to sell .biz domains without it being hooked to the business.
I do see that .biz has potential and I think that there's a lot of developed .biz sites. That's a good thing, in my opinion.
But just because it has high registration numbers doesn't mean that it has greater selling potential than .us or .info. Again, you're not even supposed to sell .biz domains without a business being hooked to it. If .biz registrars start enforcing that rule and force domain resellers to surrender the domains, there's going to be a lot of domain resellers holding the bag.
