I was actually in a SW Dev union at the last job I had and that is the very reason I left. Unions make sense for Truck Driver's or Auto workers where the skills are easily transferable, not for technical jobs.
I was in a position where there were potential bumping because of a disolvement of a group and because I was low man on the pole some guy who knew nothing about my job or .Net was going to come in an take my job away. Oh and I paid dues so that he could do
that, another added bonus. My boss was worried that all we had worked on for the last 2 years was going to be wasted because it would take at least a year to train the new person in .Net technologies since they would not have those skills.
Look what the union has done for the Carnation dairy workers here in WA, they have been on strike forever and nothing has changed.