A question about referral fees.

[Bob Jones]

I've heard that its a good idea to offer $100 referral fees for leads. But, there's something I'm not sure I understand. 

If I'm given a bad lead, should I still pay the referral fee? I'm worried about the possibility of someone giving me bogus information so that they can make some quick cash. Or, someone with good intentions could give me terrible information. I don't want to pay a bunch of money for bad leads. 

What do others do? If you pay referral fees, do you provide payment only after you've verified that the lead is good? Or, do you just eat the cost and pay for good and bad leads alike?