I don't trust them, but as long as i'm protected by alibaba which like Virosa said works a bit like ebay, i think it's going to be fine. Make sure that you find a reputable seller with lots of history, make sure that they state thet whatever they are selling is genuine(otherwise it's probably a fake and you can't get your money back), and use your common sense.

Also don't use WU or any non reversible payments to pay.

Use your credit card or paypal so you can easily dispute it if you rip. But more importantly just avoid it all by choosing the right seller.