Originally Posted by raymor

thing.com/m/ also has advantages in sharing cookies saved logins, etc with the ready of thing.com.

I wouldn't put the mobile optimized pages on a different site (m.thing.com) without a good specific reason for doing so.

On that topic, one thing to avoid, something I fine terribly annoying, is redirecting thing.com/whatever to just m.thing.com. GFY does that, so for example you can't follow links to threads or any otter pages. If you're going to redirect, redirect to the right page like this:

RewriteRule (.*) /m/$1

Or:
RewriteRule (.*) http://m.thing.com/$1