From Inside Facebook:

When users click the Like or Recommend button on a third-party website or within a Facebook app, it now publishes a full news feed story instead of just a one-line Recent Activity story. Previously, full stories with headlines, thumbnail images, and captions were only published if the website chose to implement the “Like with Comment” version of the button and users chose to add this additional context.

As the Like button now encompasses the functionality of the Share button, which Facebook has removed from its documentation, Facebook may phase out the Share button entirely. The change gives more prominence to outbound links in the news feed and on a user’s wall, and so will increase referral traffic and draw more sites to add the Like button.