You can throw keys.
They were in throw stuff earlier but now you can throw them by pressing tab button and using your arrow keys and press enter
People can’t pick up keys what other people throw.
Sometimes there are events people telling other people to throw keys, so he/she could have a prize, but it won’t work. o.o
Others can’t see that key what you can see.
Others can’t see or pick it up, only you can.
If you don’t take a key that moment you see one, it’ll appear almost every time when you go to one of the islands or beach until you pick up it.
That’s the funniest part :D It’s great to test this if you’re tourist. Next time you see golden key, ignore it so it starts doing the same than with my noob right now:
It’s a stalker key! :O