I use trade-key all of the time. It's basically just a B2B site. Both sellers and buyers can list their products and contact info there. On that site I have found lots of scammers, and some decent sellers too..
The key thing is that as with any business that you are attempting to do business with is to do a bit of research about them..
I never trade with anyone on that site whose start up date is less than a few years old. I never buy from anyone who does not accept credit cards and/or paypal. I never buy from anyone who will not supply a sample. Things like that. I also email them and see how fast they will answer that with a follow up. If it's a large order I call the phone number and talk in specifics with them. Do they gaurantee the products, offer returns,tracking info, etc..
One company I ordered a sample from, called as soon as the sample had arrived to see if I was satisfyed. This is a good indication that they have good customer service. After I placed an order they sent tracking numbers, and followed up to make sure the products had arrived and I was satisfied. With another company I received two items that were the wrong color, I emailed about them and they immediately sent two replacements free,(they let me keep the other two) and in addition I didn't have to pay any shipping...
It's basically the same no matter where or who you do business with. You just have to be skeptical with everyone and check them out. Look for the tell-tale signs and then make a sound decision based on that. You can be scammed by anyone, anywhere, so it's a must to shop by and use methods, that will protect you and your investment..