At least up til now, this doesn't seem to be a significant problem with iDeal. Any iDeal receiver will need to have at least a Dutch bank account, which requires the bank to be very sure of the identity of the person/people (UBOs) holding the account. So downright fraud is unlikely. If there is, one can file a police report, and hopefully the DA will take it to court.

Disputes between non-fraudulent entities happen of course. But I really don't like some algorithm somewhere taking seemingly arbitrary decisions on that. It usually just amounts to robbing merchants of their money, and adding some exorbitant refund fee to top it of. Settling disputes is what small claims court and dispute committees are for.

Of course, with iDeal now effectively becoming EU-wide, things may get more difficult.