So then I can't do this to add a shareThis button?
Adding Your Own Service
If you would like to add a sharing service to your blog that is not available in the standard set, you can add it using the Add a new service link in the Available Services section.
You will need to enter:
The Service name is the name you would like to use for the sharing service. It will appear in the link to the service and in the blog sharing stats, i.e. Buzz
The Sharing URL is the URL address to the sharing service. You can use the variables %post_title%, %post_url% (short URL), %post_full_url% and %post_excerpt% in the URL, i.e. http://www.google.com/buzz/post?url=%post_url%
The Icon URL is the URL address to the icon image you wish to use for this service, i.e. http://www.someserver.com/images/buzz.png
Save the service and the new service will appear in the Available Services section.