Today Facebook significantly upped the ante in its bid to dominate the way people share content on the Internet. The Facebook Like button (as an add-on for any web site) just had its first birthday a few days ago, but today Facebook gave birth to its baby brother: the Facebook Send Button.

The Facebook Send Button adds a new level of choice and privacy in how visitors to a site can share its content with others. While the Facebook Like Button automatically publishes the content to the visitor’s Facebook wall (and thus to the New Feeds of her friends), the Facebook Send Button allows that visitor to send a link to the content to individual Facebook friends (through Facebook’s Message feature), publish it to a Facebook Group, or even send it to an email address.

Here’s how sharing with the Send Button looks on a web site (illustration from Facebook Developers Blog):

The Send Button is available immediately for webmasters and developers. Click here for full instructions on how to add the Facebook Send Button to your site. The Button can be installed as a standalone, or combined with a Like Button already on your site.

Obviously Facebook wants to be the way to share content on the web. How will this affect sharing services like ShareThis.com and AddThis.com?