[koichirose]

We've been doing this for a while for a website that receives not too much traffic:

- we use a single server and the domain name determines which white label we are on.

- we use LESS and everything is variable. We load a single compiled CSS based on the domain.

- we never hard code anything, unless we know it's a single page for a single domain (everything is internationalized).

- the database contains everything and we filter out stuff a particular white label doesn't want.

This is because the website displays content (it's not a service like shopify) and most white labels want most of our editorial content, so syncing DBs is not an option (is it?). We have 40+ white labels and unless the customization is heavy we can create a new one in a matter of minutes.