Hey Ed,
I had the same concern about releasing my bank account info when I contemplated PayPal, but then I just did it. That was nearing three years ago and thus far not a single concern... I know there is always that possibility, but I don't think I'm being naive to continue in the electronic money transfer era.
I electronically pay both PayPal and eBay, SBC, both of my credit cards and my mortgage. Actually in retrospect, the prospect of fraud would be more embarrassing than anything else as there is seldom any money in the account!
As a side note, last year in reviewing one of my credit cards, online, I noted four purchases all the same amount. Odd. Closer scrutiny bore out that there were eleven transactions that were not mine.
The credit card's customer service department identified the nature of the purchases and the rep dug a little further and traced the routing of the purchases through England and China. Very sophisticated and had I not caught up with it, maybe it would have become some staggering amount, but as it was, the credit card issuer cleared me of responsibility right on the spot, the account was closed and the legitimate balance transferred to a new card, which I received with seventy-two hours.
End of the month, I read my electronic statements, pull a charred stick out of the fire and scribe the information on my cave's wall.