I would probably click "yes" if it's < $5.
Not for every FB 'friend', but there's a 'sufficiently close' threshold where, yes, I'd click that button. Even better if it's day-of fulfillment. And I bet I'm not alone.
Try making your birthday private in Facebook one year and see how many happy birthday messages you get when people aren't prodded by Facebook to care. It's a lot less.
I probably only post 10-15 "happy birthday!" posts a year. So every day I check to see who's birthday it is. If it's someone I'm close to, then I post something.
If Facebook didn't have them displayed, I would probably have those 15 birthdays written down on a real world calendar, and I'd just check that.
Going to try an experiment where I make a random day my birthday, delete all the posts that catch on to the fake birthday, and then change it to a month later. Will post results.
Not to say that you're less thoughtful for using Facebook reminders; it just seems to promote shallow interactions at times.
The greatest gift you can give someone is your time.
I think you're right that it's "sufficiently close", but I'm struggling with how I define that. It's essentially someone close enough that I would give them a gift, but not so close that giving them a gift through FB is too impersonal.
Do you have friends that you call or hang out with on their birthday but don't write on their wall? Most of my fb well wishes are from loose connections. My real friends call, text or hang out with me on my bday. Facebook is the least personal touchpoint I'm available through, but maybe I'm an exception.
PS - I think it's been said, but combining gifts is probably the key here(i.e. everyone chips in to get you something).
[1] arguable?