If you have auto return is enabled and you have enabled the PayPal account optional at checkout (pay as a guest), the buyer is not automatically directed back to your web site after completing their payment unless he or she chooses to return to your website. In other words, PayPal at the point is offering the buyer a chance to open a PayPal Account if they want to, else in order for the buyer to return to your site, they must click on the return link. If the buyer has a PayPal Account and uses it to complete the checkout, they are automatically returned to your site. PayPal is always looking for new people to open an account, this is their way of offering that opportunity.
