What's stopping people from charging back? Is there any defense for it?
Well, I think I scambled the use of the words.
eChecks not clearing is what we're talking about and there's no defense to it.
"Chargeback" in paypal terms is when the money clears, but later the user makes a claim (and for virutal goods, their only valid claim is card was used without authorization), and this is ~1% that goes through.
There is also a reversal which is when paypal thinks there are funds (usually someone with paypal tied to their bank account but then when paypal tries to pull the money, there is insufficient funds, stc.) and this for us is very, very rare.
I know it's natural to want to protect from those that will steal with knowingly bad eCheck fraud. But, even if you experience an insanely high 10% chargebacks on the eChecks... that means 90% went through fine. I would just consider it the cost of doing business and wouldn't want to stop the 90% from experiencing the immediate gratification.