Are proxies not secure at all ?

Does it make sense to worry while loggin-in in some of your account (email / cPanel / domain-registar / etc ) using a false IP of some proxies ?

If you need to totally hide your identity while registering at those services you need a counterfeit IP, but aren't you concerned about your login details ?

For example how do you register (and pay) a new domain or hosting account using a fake IP ?