As in real life, there are always going to be unscrupulous people willing to take your A$ if you are willing to offer it ... and I have heard of many being parted.
Ideally my advice would be don't give it to the tarts .. with out a market .. they would go out of business.. but there is a market here otherwise it wouldn't flourish... and it obviously does for whatever reason.
Maybe guys like the seediness of it, maybe some guys havent got or cant be bothered to learn the social graces .. we have all met the Cookie Monsters at some point
.. who knows ... the thing is .. it does exist and is likely to continue to do so.
A black list of girls who make the promise and then do a runner will always be difficult to ensure is true ... it could be a clash of personality or a dispute after the gifting is complete and they are unable to return the gift as gifting men is not allowed on here.. as well as being dishonest to take your A$ in the first place.
I'm sure it happens the other way too, girls in good faith room and the guys refuse to make good their promises too.
Gift because you want too, and expect nothing back. If you pay for services there is always the risk of losing out and I'm afraid you will have to put it down to experiences if they are not made good. There is no facility for redress.
Offended parties could always advertise on their profile descriptions to warn others of the unscrupulous & report the antics to Support in case there is a pattern of behaviour emerging..
A blacklist could be used for revenge on innocent parties and I don't believe is the answer here for this problem. Don't pay would ensure you are not parted from your A$