Not everyone wants to share everything. So this could be a great personal analytics tool capture life and build a better self. Then anything you don't mind sharing could go into a more public social network. I like the idea of a private timeline.

In the Reddit AMA Kevin Rose said he thought "Quantified self (eg. fuelband, fitbit)" were the next trends. So a Quantified self timeline would make a lot of sense and bring things together quite nicely.

Good luck with this and excited to see how this progresses.