I don't say you're an impostor :)
I just say all this sounds more like "conference" (= prof) than "hacker space" (= hobby)
Both can be fun.
I'm from Stuttgart and going to the Shack is a whole different experience than going to any meetup or conference.
They are all hobby, on top of my work time. Many of the attendees are there for fun, especially on eurucamp, off their own pocket. Obviously, 3 days of meeting with 300 international people isn't going to be all random (even things like the CCC only _seem_ hackish).
I do help and attend spontanous meetups of all forms and fashions as well - still, they all have rules and they are all better for it.
On the peak, we ran a 5-day conference set with a one week program around it only on voluntary work.
We currently have an attendance that is very diverse (we don't count) and we worked for that a lot.
It couldn't be any less professional and if it can, we'd like to remove that.
http://2014.eurucamp.org/concept/
The Elasticsearch usergroup is run at a small community-driven coworking space (and existed before Elastic, the company) and the Rust usergroup definitely has no professional outset.
I also ran devrooms on FOSDEM.
One of the meetups the Ruby Berlin e.V. runs (the governing body for all of this) has _3 full talks_+Lightning talks every month, without any company involvement other then providing rooms.
Suits are really of no interest to me in this case.
Also, I'd like to say that I'm not discussing from a theoretical point here - I've been doing community work for more then 10 years and have put all the things I say here into production at some point and in multiple contexts. With measurable successes and failures.