The caveats of riding someones coattails

Question for the hivemind. Mods please move if this is the wrong forum.

I see various "drop off your ewaste for free" events and most of the time these are held in the parking lot of a retail chain.



Has anyone parked thier truck in the same area and with a sign offered to pay for ewaste that people are going to drop off?

An acquaintance of mine said he used to do the same thing back in the day when a buy your silver and gold company would visit an convention center.

He would hit up the lines and offer to buy anyones precious metals at a higher rate. Then he would take the loot to a nearby refiner and profit.

This is not meant to be a troll or flamebait, but I am fishing for some cons of doing such a thing.