This is what Facebook had to say:
"A year ago, we launched the Like button, which gives you a quick way to share the things you find on the web with all your friends. But there are times when you find something that you only want to share with a few specific people. Say you're on Orbitz and want to tell your roommates about a great idea for a summer vacation, or you come across a Huffington Post article that you only want to share with people at work. With the new Send button, now you can share things with any of your Groups or individual friends on Facebook."