What do people use public suffix for?

Mon Apr 15 13:10:17 UTC 2013

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.