I understand that it’s not possible to add metatags to the head of a WordPress.com blog. I would just like to request that a feature be added similar to the Google and Bing webmaster tools that allows you to input a content value that Facebook provides at the link above. Here’s what they say:
Get Insights for your Website
Add a meta tag to your webpage
Gain access to insights for your website by adding a fb:admins or fb:app_id meta tag to your root webpage, linking it to your personal account or an application.
The metatag looks like this: <meta property="fb:admins" content="12345678910" />