Unless you’re trolling I’m not sure why you’d even ask this question.
You can return almost ANY electronic device to almost ANY STORE (at least in the U.S.) as long as it’s within a reasonable period of time and the only thing you need do is say “it doesn’t work for me”. Even stores which have technical staff (like Best Buy – ESPECIALLY Best Buy) don’t really care except to fill out a line on their form.
I’ve returned dozens of various devices and never had an issue – no one will grill you, you don’t have to have proof, because in this very complicated world we live in there’s no way any device can possibly satisfied or work with the expectations of so many tens of thousands of different setups.
I only wish I had returned my AppleTV within the right time period – the Live is so much more amazing I ended up buying another one (speaking of which, if you actually CAN’T return your product and do end up eBaying it be sure to post here and let us know, as I can really use another).