As stated earlier, unauthorized=fake.
Sample pairs are usually sent to the buyer of a shop/chain. Nike's way of saying "hey here is a shoe that we're releasing and this is what it looks like in hand." In other words, "hey, buy them." Samples can come in any size, but they usually come in a size 9/9.5. That size is more pleasing on the eye. Mind you, for the most part, Nike doesn't request that you send them back. So if you wear the sample size you're in luck.
People get early access to shoes, because some retailers don't adhere to the set release date. Some of these shops get them ahead of the release date and put some pairs up on consignment sites. Also, theft. Let's say Nike produced 50,000 pairs of the Air Jordan V. From point A (factory) to point B (Nike warehouse) 50,000 pairs are not showing up. Those stolen pairs end up in the hands of the connect. I remember when I worked at Niketown NY, we were receiving a shipment of True Blue 3s (when they were first retro'd). When we opened some of the boxes they were filled with tires. Those missing pairs most likely went to someone's connect.