True? If so, does it matter? Let me answer that. Nah.
I'm a half-hearted member of the Facebook world. I have only posted a couple of times, although I comment on friends' posts occasionally. I have very few Facebook friends and some of them are people I've never met ("friends" I picked up when I was addicted to FarmVille or FarmTown or some farm things). So the fact, if it's a fact, that posts only reach 12 percent of a user's friends doesn't bother me at all. But I do think it's kind of interesting.