I'm surprised they weren't already in one. I worked at a competitor (the Wall St. Journal) years ago and all software engineers there had to be part of the union. Unions in the news industry are extremely common and powerful. My subjective experience with it was that union membership was mostly inconsequential for developers. The market for programmers is so strong that people would just leave if they weren't treated…
This of course isn’t a problem for HN posters, who are all 10x engineers or w/e. Overall though, not having a contract, recourse and representation in a large company is a pretty big risk factor unless you just toil away in silence.
Why? I have an in-demand set of skills and could easily find a new job if I wanted to.
I'd much rather negotiate directly with my employer than have a union intermediating that relationship. If anything, it feels far riskier to have a politically-motivated union boss control my employment.