this sort of goes against one of the philosophies/purposes of 'timeline,' namely a journal of your life along with all the related connections you may have made. you may be able to hack something, but is the gain/ROI really worth it?
Considering Facebook has been around for quite a few years now, I don't think it's that rare for people to look at what they posted five years ago and decide they'd rather keep that in the past. Especially since they had no idea at the time that timeline was going to happen.
It depends what you want your Facebook to be. I want it to be a way to keep in touch with my friends. I don't want it to be a publicly-accessible journal of my life. It's as simple as that.
Do you think everyone is an extrovert and likes that idea? Do you want your life to be an open book to all of your family and friends for all the way back to when you joined?