I just browsed through this thread and found so many numbers that I thought I should make a graph displaying the interrelation between time and friends (or "likes") on Flightgear's Facebook page. Here's the result:
It doesn't only look pretty linear, it is. The correlation between days and friends is 0.993, which is incredible considering this displays human behavior. I ran a regression and it predicts 19.25 friends per day over the whole period. Since the curve flattened off after March, I ran another regression with data since April, but this still predicts 18.1 likes per day.
No end in sight! Let's rock this on!
David