I am in the early stages of thinking through a product I am looking to develop, the product is a hosted e-commerce solution. What kind of things do I need to think about when allowing users to register there own domain names? Hows does that even work? I know I can do subdomains, but no idea how a users own domain would work on the hosted solution?
Any ideas?
You can run multiple domains on a single host using virtual hosts, as supported by HTTP 1.1. See the Apache docs for setting up virtual hosts for Apache httpd for example (you may use some other web server).
You probably don't want to get involved with the actual domain registration: users should register the domain with an established domain registrar and configure the A record to point to your server.
All a user would then do is specify their domain name and you'd update Apache's httpd.conf (or equivalent config file) appropriately.