I would report your facebook posts as abuse if I saw them on my newsfeed, most likely. "I joined a bunch of groups so I could advertise to them." Scummy.

Not all advertisement is scummy.

You could easily change the tone here. "I joined a bunch of very specific types of groups so I could manually write a post that tells them about a free app that I built for their demographic."

I felt the "scum" right away, but then I thought about the source of the feeling. Scummy is when you write bait. Telling people about your app - sometimes that requires a door to door cold call.

I think this app deserved to be shared with that group, and it's particularly un-scummy considering the fact that it's brand new, free, and isn't trying to mine for email addys.

thank you! took the words right out of my mouth

The groups he sent to are quite likely to actually use and enjoy the app.

Many others might whether you believe in the product or not though. I guess I am looking for less intrusive and disruptive way to acquire user, but the downside to this is that it is way harder to gain users. But I think your facebook group selection was smart. A lot of freshmen would like this app.