It seems to me that printing coins is mathematically the same as “demurrage” except with an inflating money supply (if you force the money supply to always return to same amount, printing coins will mathematically become “demurrage”).
So, it becomes clear that what a person is getting as UBI in their “person coins”, is money taken from the people who trust them (and thus may hold “person X coin”) and then given back to the person X.
To me it seems like Circles is single-hop redistribution in a web-of-trust. Is this correct? Thus it is comparable to person X asking their 16 friends (if we assume each person has on average 16 friends) to donate money to a UBI fund every month. Maybe something like 60 dollars per friend, roughly 1000 dollars per month.
Note, it is technically possible to achieve multi-hop redistribution in a web-of-trust. This is implemented in full here (includes a solution to “stuck payment attack” that is the main obstacle historically for decentralized multi-hop payments, a solution Circles could also use). Thus if Circles is single-hop redistribution, two categories can be recognized: redistribution in web-of-trust by single-hop vs by multi-hop.