It could be an interesting cybersecurity technique to hide obvious crypto private keys all over.
If it gets swept you are breached.
Yeah, just keep dust in it. Like $10
Only works for low value targets, where you don't have to trust your coworkers. Probably need to rotate the key daily, which possibly adds transaction costs. You would also need to set up the detection capabilities to be able to figure out the intrusion path, or the flag is pretty meaningless. And at that point you may just as well put tripwires onto sensitive files.
There are entire businesses set up to help enterprises do this at scale: https://canarytokens.org/nest/