Different email account is all you need, doesn't even have to be a google email. I heard some people have got blocked from excessive use but if you only buy something every few weeks or so you should be fine. I've probably bought 6 things from buy.com this way, I usually only use it if I plan to buy something, not just to go look for random $10 items I don't really need.
It's awesome for video game items under $30 since buy.com already has pretty competitive pricing, and for -$10 it's hard to beat.