I use Paypal and my debit card all the time for online purchases. I have never had a problem yet....knock on wood. One option is do what my DH and I did. We opened a seperate checking account that we use only for online purchases and nothing else. We keep a very mimimum amount in that account just in case our card or number is ever stolen. We transfer funds between accounts as needed. This way it gives us a little more sense of security knowing that if someone stole our number they wouldn't get much out of it. This has worked for us for over 5 years now.