Regardless of the overtly underlying intention of the Timeline being to sell perfectly pitched products not only to your personality; but also to your nostalgic conscience, this does also bring forward a different use. Recently passed Steve Jobs made this quote at his Stanford University Commencement speech: "You can't connect the dots looking forward, you can only do so looking back." This idea of clearly seeing the dots connect throughout your activity is something that has consumed my evening. It's a deeper bond with the product beyond the mere shine of technological advancement. I'm not saying fill out the whole timeline of the years between birth and activation of your account. Such a thing seems idiotic to me; but with what information there is (three years for me) watching the step-by-step development of one-self can be difficult to see, especially with the sketchy history as a student I have had. But such a functionality, the translation of data into the tightly compiled stories is something that can't be found anywhere else at the moment. The Timeline encompasses Facebook as a product with a characterisation: a narrative of what it is, instead of being the network of experimentation and attempts to define itself through analysis.
Look past the ads and take care of the transparency of your data and you have yourself a novel idea of individual definition.