There have been people making profits on social gatherings for a long time. A restaurant will be happy to host a party for you. A bar will want you to come in and socialize. There’s nothing fundamentally new about FaceBook. Instead of paying for food or liquor, I’m having ads pop up and (if I feel like it) providing information and photos and maybe apps and whatever.
Similarly, I’ve contributed on StackOverflow (and have a rep > 10K) and Wikipedia. Answers and corrections are not something I feel I need to treasure. I can always have more ideas and write more stuff. I get a good feeling when people like what I’ve done, or benefit from it, and this is a quick and easy way to get that feeling. I’ve coded on what would have been an open source project if it didn’t have a noncommercial license. Again, I didn’t get a dime, but who cares, as long as it’s something I like doing? Nor do I feel this is like sharecropping, as there’s no obligation involved.
There are limits, of course. Like many people, I don’t want to feel ripped off, and this includes free labor to enrich others more than I like. (I believe this is one reason for the popularity of the Gnu General Public License.) I don’t want to feel like I have to do something I’m not getting paid for.
My advice would be to do as you like, and not worry overmuch about people making money off your contributions. If you feel you’re being taken advantage of, or it stops being fun, stop.