As a consumer of the web and a developer on the web, Mozilla is one of the few "big" players in the web ecosystem that I see who are really fighting for keeping the web open.
We were just having this discussion with a friend the other day, on the topic of the anti-trust hearings. What if the web didn't evolve to be open like it was today, but instead had followed the evolution of the mobile space, dominated and fully controlled by only two players? What if it was impossible to run a website from a server in your bedroom but instead had to submit your website to some corporation and wait a couple of days before some semi-human reviewer approved it (or not)? The transformative power of the web on global society would never have been as big as it has been if it had evolved in that model.
For that reason alone, I applaud Mozilla and I decided to start donating today. I would hate for the web to be under the tyranny of some corporation because that would be such a loss for humanity. And we need people and organizations that put up the fight against the Googles of this world.