I figured my post would ruffle a few feathers.
I used to deal with the local refuse company - they bought from me, and I employed their services. I knew the owners quite well. The "dumpster diving" question came up a time or two. Here's the "rules" where I was.
I contract with them to provide the container, which they place on my property. As long as it's there, the contents of the container are mine. I can add to or remove any time I want. Once the container is loaded on or emptied into their truck, I no longer own the material - it's theirs. At no time does is become public property.
Now the perils of dumpster diving. These examples are extreme and have nothing to do with speakers, but I think you'll get the idea.
A large hardware chain that closed down in the 90s had a distribution warehouse in the nearby town. I did alot of business with their maintenance department. I was in their yard one day, and spotted a roll-off box with two guys throwing in pallets of those cheapo 2 ton garage floor jacks. It seems that some had serious defects, and there had been several accidents (including a death if I remember correctly). Since they were imported, the manufacturer shipped they replacements with the flaw corrected, and instructed them to scrap their inventory, as opposed to shipping them back overseas. My buddy who worked there also told me that they had hired a guard for that night to prevent any thefts until the scrap company could pick the box up the next day.
The second time - I went with a customer to a nearby scrap yard where he bought good used steel for repairing his farm equipment. I wandered around, and spotted a huge pile of trailer hitch receiver tongues and tow hooks. Since I sold new trailer hitches in my store, I asked about them. He said they came from a nearby manufacturer, and they had failed their x-ray / mag particle inspection. They had some theft issues, and were loading them up to haul to the port for destruction. Imagine following a trailer down the freeway when a defective tongue that someone bought at a flea market breaks and comes straight at you.
I'm sure some of you have heard about some of the counterfeit hardware and parts that the government bought and used. Unfortunately, some of that slipped through their fingers and got sold at auctions. I even ended up with some of it that I scrapped. That's why any "surplus" items the government buys back requires traceability on the item - part number, sale and lot number, etc.
I doubt a pair of speakers would ever be an issue, but you never know the reason something is tossed. Better to ask, or leave it alone. Not worth taking the chance. Who knows - you might pick up something that's stolen that later comes back and bites you in the butt.
