More information at http://waterjuice.org/2019/08/21/oh-my-oid/
Can I have more than one? - You can click the button as often as you want
What do I do if I don't want it anymore? - Nothing, just stop using it.
What if too many people click it and they run out? - Seems unlikely, the number will just keep getting bigger.
Why don't I have to register an account or provide details? - Because there is no need, OIDs are not that precious.
Is the OID I get real? - Yes.