There are many reasons why it’s a good thing to join the Moodle Users Association, MoodleNews posted a pretty good roundup here. Everyone will have their own reasons for doing so. Some people want to give something back to Moodle, some want to vote on features and impact the development of Moodle. Now it’s no secret, I make my living using Open Source tools, predominantly around Moodle. So I’d be crazy not to give something back.
I am not a Moodle Partner (maybe one day), and I realise that my individual contribution of 100 Australian dollars is just a drop in the ocean, but collectively, every contribution adds up. I contributed not for votes, I joined the Moodle Association because I want to help prove this HQ-backed “crowdsourcing” concept works. Regardless of how much revenue it generates, it will generate ideas and spur innovation. And that has got to be worth every penny.