E-commerce Predators

A common warning to all who participate in the social networking sites was not to put to much personal information on the sites (e.g., profile pages), so visitors with unethical or immoral motives can't make contact or create false identities. Makes sense to me. But soon after, I had a funny feeling in my stomach. I do not have actively participate in any social networking sites like MySpace or Facebook, yet my information lives on megasites such as Amazon.com and Walmart.com to name a few. We are all aware of the security features that supposedly safeguard our info with encryption, and so many of us continue to buy safely online. Aside from privacy settings, do these social networks offer the same type of protection for its users?

If e-commerce is becoming more acceptable and trustworthy despite possible identity theft (predators), why should people worry so much about Facebook and MySpace security? I don't know the answer, and though I write this, I don't see myself joining any of these popular networking sites any time soon.