[Zikes]

Sometimes people drift apart, not all friendships last forever. It's entirely possible the same thing would have happened with or without Facebook.

Regarding your feelings towards their new "friends", you've no right to question their friendship or its value. Those are real people on both ends, no matter the means in the middle, and you should respect that. All of my best friends I've met online by way of various sites. We've only seen each other in person a handful of times, yet they know me and I know them better than anyone whom I interact with face-to-face.