If I where Facebook I would rethink Calender.
Turn it into a "future timeline" and add goals, to-do's allow for easy calender integration.
That way they might now own actual intent, but future intent.
Going on a trip? (find cheap tickets or hotels)
Loosing weight? (here are places, products & diets)
Going to run a marathon (products, books on training, websites to join)
Planning bachelors party? (events)
Bought a ticket (add to calender and propose things to do before)
Then their data would begin to be interesting and they would own a type of intent that Google doesn't (Because they mostly lack the proper context).
Right now the calender is primarily around parties and conferences. Expand that then at least I think they would have a chance of providing relevance and would have better time finding out when to present ads.
I see a few attempts but they need to re-do it completely.