If you do you're making a huge mistake.
I am not a Facebook super fan. I annoy and am annoyed by just as much of the stuff I listed above. But it does not change the reality that Facebook is currently the largest networking site on the planet. For better and for worse it has become the hub around which most people congregate.
Can you afford to be absent? For some people with infinite resources and no need for networking I could understand. But are you one of those folks? I honestly cannot think of a single person who fits into either of those catagories.
There are no infinite resources. And most of us are just a few pay checks away from needing some sort of networking (social or otherwise). The obvious exception is old people who live their lives outside of modern technology.
Your great grandparents might do this. That sounds kind of rude but I can see how a retiree who is set in their ways might want to avoid Facebook. They probably won't be looking for a job any time soon. Then again, both of my parents love being able to show off photos of their grandkids on Facebook.