A lesser known tenet of the free software movement: "You can have control over a program someone else wrote (if it's free), but you can never have control over a service someone else runs, so never use a service where in principle a program would do." - gnu.org/philosophy

But when exactly would a program do? I will dig into the details and examine popular services so that you can gain confidence in evaluating services you encounter.

Finally, I will dip into other dimensions of judging services, such as how they treat your data.