Subscriptions to either free or paid cloud services will continue to climb in the years ahead, jumping to an estimated 625 million next year, and then doubling over the course of four years to reach 1.3 billion by 2017, as shown in the figure below. 1
Whether it’s a “free” email” or any other online cloud service you can count on that the information will be used to gather information about you. Whether it’s the mail being part of an ad-network or the just storage leaking info 2.
There are of course ways to avoid the tracking, but they’re mainly by going off-cloud 3.