I would argue that Alibaba isn't "nothing but scammers". In my experience it's just that scammers tend to flood the categories that MOST new sellers look at, such as high value consumer electronics (phones, ipods, consoles) and branded clothing. If you were a scammer do you think you'd make more money pretending to sell games consoles or doorhandles? I'd bet games consoles - there are fewer around, the demand outstrips the supply and they're higher value. Now, door handles, that's an idea...
I reitterate my original question:
Do Alibaba introductory videos indicate trustworthiness?