I'm getting ready to have my website redone with Joomla 1.5 and a 3rd party shopping cart which is NOT a Joomla component. The dilemma I have is regarding user registration: I want people to have to register to be able to access some free content on the site. And of course people will have accounts in the shopping cart. If I have a bridge created between Joomla and the cart, then if someone registers in Joomla, then they also become registered in the shopping cart and vice versa. The problem I see is that not all people who register in Joomla will become actual paying customers.

Do you think it's better to just keep the two systems separate? And perhaps justify having two logins as a security measure, "for your added safety" or something like that?