My friend is a H.S. Biology teacher. He told me a story that a student stole an old vial of mercury from the chemistry lab, and when it was discovered missing, he was surprised as to how intense the investigation as to it's whereabouts would be.
He tried to dispose of the evidence down the family bathroom sink.
Of course, it all sat in the P-trap.
They had over $40,000 in plumbing replacement, municipal fees to have their sewer line dug up and replaced, and environmental testing.
A co-worker of mine was invited to pick through an elderly neighbor's home for tools and "guy stuff" before he went to a retirement/nursing home. One of the things he took was a 10lb crockery jug, with a cork, of mercury that dated back to the late 1800's early 1900's. He new it was dangerous, only handled it with gloves etc.
He eventually decided he'd just turn it in at a local Fire Dept. who collected hazmat, paint cans etc. When they found it was mercury, they flipped out, called the actual hazmat team, the health department and the police.
The health department wanted to take him for a blood test, and when he made noises about politely declining, the police moved in with cuffs, and noises about getting a warrant to inspect his home were made too. He did some fast talking, agreed to come in for a blood test at a later date after they had all his info and thankfully made all the fuss go away.
IMO, if places did pay spot/market prices for Hg, it would do a lot to get it out of circulation the environment IMO. OTOH, there might be more danger from people scrounging for it, then having a spill etc. but I think in the long run it would get more out of the environment than spread it around.
I can't remember where it was, but one person had a tale that his father worked at a gold mine, and one of the activities they let you do was put on waders and step in/on the mercury tank used to amalgamate the gold out of the ore.