Well, it is hard to say but, trust no one there, but trust in your instincts of not getting scammed, now this site puts effort on avoiding a bad reputation as man in the middle, so very often you will get your money back using MercadoPago, thank lord I haven't got scammed, but maybe it is because I buy stuff that it's not "too good to be true deal" like recent iPhones or computer 50% off or less. I would like to advise you to have your correct address always, use MercadoPago, do not buy documents or services to get documents, preffer "MercadoEnvios" with DHL or FedEx and look for the user's reputation or if it's about a new user look if it is his first or second sale, then use MercadoPago with MercadoEnvios, and make an effort to have communication with them to explain the user how this method works for the sake of both, if the user refuses, then agree to cancel the operation, DO NOT MAKE DEPOSITS TO THE NEW INEXPERIENCED USER, unless, you think it worths to give it a shot, I personally tried that buying an Nvidia GTX650ti and got it pretty quick, buy again, that was a safe deal, normal item, new user wanting to get rid of it, and the price was fair for the time.
In the end. you always have the last word as final user just as I do with my very own experiences.
Hope this review helps!