Potential issues: - There are some well-known ways around developer verification (peopl in some countries _need_ them for one reason or another so - they use non-local cards,etc) - it's very basic verification and people who pay for ads likely arleady do it (payment have to come from somewhere). - Proof of address is also spoofable and there are some situations were people making/providing fakes when they don't mean ill intent towards anybody else (example: Russia, some of ways to make non-Russian-only Visa/MC require making fake proof) but such methods could also be abused for doing actual harm. - ID verification sometimes complicated if a lot of countries are involved. Example: I'm not at all sure at least one person in Google actually knew what Abhazian passport is and how to verify it ?