Provider-based DNS naming?

This may not be the right forum for this request, but if not, I 
apologise but you might be able to point me in the right direction.

What is the prevailing view on "provider based" DNS naming on Internet.

I.e. is there something that can be done to disuade a provider - say
provider.top from registering his customer companies as

	company1.provider.top
	company2.provider.top etc..

and thus attempting to lock these companies into their services (refusing
to rewrite their mailing addresses as name@localhost and honoring MX'es
for company.top pointing to provider.top).

Do you know of a RIPE/ISOC documentation on this issue - or is this 
behaviour generally considered so obviously stupid that no one has
thought of mentioning it?

Thanks in advance

Marius Olafsson
SURIS/ISnet