Online Yard Sale (Pick-up on Saturday)??

We have a new trend for our area it seems.  Don't know about other cities / locations.  People are doing I assume Facebook online yardsale of items.  Then every saturday morning everyone meets up at the Walmart parking lot.  I saw this a week or so ago and had thought it was a school type "trunk" sale.  One of the customers came in the store saturday and told me it was the online yardsale swap spot.  Anyone done this?

That's strange that Wal-Mart would allow something like that in their parking lot.

The space isn't owned by Walmart, they are just a tenant.  The cars are next to a line of spaces next to the Walmart gas station.  Those spots almost never get used as they are far from the store, the other retail stores in the strip, etc.  Maybe they figure people will stop and fill-up whiel they are there picking-up.  Who knows.