[eikenberry]

I'm not sure as I don't belong to any of these but here are some examples (US) that seem like they "work well"... Screen Actors, Directors, Writers all have guilds. Real-estate and Lawyers have decent looking guilds, they just don't call them by name. Doctors, Dentists and Nurses also have guilds (they call them associations).

[thylacine222]

SAG, DGA, and WGA are all labor unions. The other cases I'll grant you, but it's less clear what their direct benefit to their members is besides acting as lobbying organizations.

[peruvian]

SAC, WAG, etc. are all labor unions similar to the one Bandcamp just created. Don't be confused by the name.

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As for the other examples, what I like about tech is that anyone can join the industry. I think the way attorneys and doctors have set up their profession works for them but it really makes it hard for anyone who didn't choose the golden path to join.