We've answered the friends question here: Lost friends list.... & How does the points system work with new site?
As for groups, we migrated groups that had more than one member and/or content created in the last 6 months. We had over 300 groups, and more than 225 of them were "ghost towns" that had nothing in them. If your group fell into this category, it has been deleted. If it wasn't, please let me know which one it was and I can check into it for you.