Best Practices for Managing E-Commerce Customer Data

I am wondering if anyone has some best practices regarding managing customer data from their ecommerce site. Specifically, customer and contact records. Currently, any time a contact registers for our site they are created as a new customer and contact in Netsuite - even if when they register there is a duplicate in Netsuite. It is my understanding that the reason this was initially set up like this was because we have companies with multiple locations and the contacts we deal with at each location might only manage that specific store so we wanted to treat them separate. But now