Read the blog post -- Twitter OAuth Comes to Second Life
Excerpt:What this  means is that you can now let people Tweet from within Second Life in a safe and secure way, without having  to set up external Web servers, and without requiring Residents to  re-enter credentials if they want to use Twitter from inworld.
We believe that our merchants can build incredible new products with this functionality and that the shoppers will love it and will soon be searching for these products.  The owners of items will be in control of linking these items to their twitter account and will be able to turn access to individual items on and off from their twitter accounts.
Regards,
The Commerce Team