In general, yes, I do trust MOST ecommerce sites with my details (I'm assuming you mean card and bank details) but that doesn't stop me taking precautions. I have a couple of bank accounts, one of which I have linked to my PayPal account. That account is used solely for my online shopping and is in credit only to the amount of money I want to spend online and usually I use PayPal to pay for my purchases. For any purchase over £100 I use my credit card which is protected against fraud by my CC provider. So far so good, I haven't been scammed in the seven or eight years I have been doing it this way (touch wood).