Answer:
A mechanism to discover who is following you.
It belongs to you but you donβt use it. It does not belong to other people but they use it. What is it?
Some keep it in a dumpster while others keep it in their trunk.
What gets bigger the more you take away from it?
These are believed to be found at the end of rainbows
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.