I think the punchline here is that it is a Sisyphean task to find (or expect) a "free" web service that doesn't already profit from user submitted content.

I don't think it is making light of people who are annoyed/boycotting... It is making light of the line of thought that companies we give our data to (for free) are ever going to use it for what we want them to, and not what they want to (make money).

This comic is saying that if we care about the rights to our work, don't give the work to anyone.