fast tech sells many clones and knockoffs and from what I've seen on other forums - eGo types sub forum, for example - is that there is a percentage of DOAs and disfunctions happening but the difference in price may be worth losing a few here and there. Some have not had any problems and some have 70-80% good items. I don't know what their return policy is.
I've had good luck buying name brands from heaven gifts, health cabin and eastmall and their customer loyalty rewards programs pay off in the long run and can more than make up for the shipping charges, but it takes a while to build up the points. Their return policy is usually 6 months but you'll pay for the return shipping. I haven't had to use that much in the last 4 years but when I did, I chose the least expensive postage and it has worked out well.