As someone who worked at Boo.com - escaping in Feb 2000 as its death become obvious to anyone, I don't think boohoo.com capitalises on boo.com - most people have never heard of boo.com..
I have to say though, boohoo.com quite clearly capitalises on boo's branding and history.
In fact, if I'm not mistaken it originally mimicked the typeface and name of Ernst Malmsten's book about the boo.com story, which is kind of ironic given the circumstances.
Book:
http://t1.gstatic.com/images?q=tbn:ANd9GcTPf1rQbytroVo7SYUhV...
Boohoo logo (now):
http://www.boohoo.com/content/ebiz/boohoo/resources/images/l...
(To be fair, Boohoo have altered their branding over time but the similarities are still recognisable I think?).