LayeredTech (www.layeredtech.com) are pretty tough on assigning IP's to you. They follow the ARIN stuff to the letter pretty much.

For most people it isn't a problem, but, for those with the 'IP per site for SEO' idea it can cause problems - as ARIN don't really accept that as good justification

ARIN can audit dc's IP records at any time - and the DC's themselves need to show ARIN they are using their ips (and how they are using them) before they can get further IP's from them. Fits in logically the DC's would then adhere to the policy.