We offer white-label resellers with private name servers etc but many of our clients don't take us up on it and are more than happy just to use our own name servers - it all depends on the customers requirements and usage of the reseller, everyone's different. If a resellers client looks hard enough into it 9 times out of 10 they're still going to find out who the main reseller host is. I'd like to think our reseller clients are honest about it with their customers if they do ask - but that's up to them.