Personally think about talking to other hosting supplier and/or friends if your only a small hosting supplier on the net, only. If you're not only on the net (i.e. a limited company, or plc, etc), fruad detection would be a great idea. Its entirely up to you how you put it - I see it as they pay the bill, no problems - but whenever I've owned a web supplier, I've always made a relationship with my clients so they are not just a billing number on our billing system.