Remembering someone's birthday used to mean something. You'd write it down in your calendar and then call or send a card. It was a thoughtful act and took time to complete. There was a cost to the transaction (time at the very least) and this sacrifice was inherently part of the meaning.
But now, thanks to Facebook it's meaningless. You see it's my birthday in passing. Quick notes on my wall. Maybe gift me a digital plate of nachos, astronaut or whatever other collection of pixels are available that day.
Mark my words - there's gonna be a retro boomerang here. Maybe it won't be back to paper greeting cards but there will be social gestures representing scarcity that will become popular. Some way to prove that my thoughts for you were more than a superpoke. Because they cost me something - time. money.