blogs.law.harvard.edu also belongs to harvard.edu, so what's the problem? Many universities give blog space (and email accounts) to alumni, as a way to keep them engaged (and hit them up for donations...).
ISPs and other services often give customers customername.isp.net... - I do this, customers get username.xen.prgmr.com, while prgmr.com is for official business stuff. most of the stuff on something.xen.prgmr.com has absolutely nothing to do with prgmr.com, other than paying me eight bucks a month or what have you, so marking a something.xen.prgmr.com link with 'prgmr.com' would give people the wrong idea.