What do people use public suffix for?

[johnl at iecc.com (John Levine)]

The public suffix list contains points in the DNS where (roughly
speaking) names below that point are under different management from
each other and from that name.  It's here: http://publicsuffix.org/

The idea is that abc.foo.com and xyz.foo.com have the same management,
but abc.co.uk and xyz.co.uk do not.

You don't have to tell me that it's a gross crock, but it seems to
be a useful one.  What do people use it for?  Here's what I know of:

* Web browsers use it to manage cookies to keep a site from putting
cookies that will affect other sites, e.g. abc.foo.co.uk can set a
cookie for foo.co.uk but not for co.uk.

* DMARC (www.dmarc.org) uses it to find a policy record in the DNS
that describes a subtree, e.g., if you get mail that purports to be
from eBay at reply1.ebay.com it checks the policy at ebay.com.

What other current applications are there?

R's,
John

PS: Really, you don't have to tell me what a crock it is.