What really disappoints me is when unions make demands unrelated to pay or work conditions, but to restricting competition. See LA teachers union and their demands to cap charter schools. This is a direct demand to punish teachers who are not part of unions. This is a stark reminder that unions is a "fight coercion with more coercion" solution.
It is important to remember that economic coerciveness is a result of overwhelming scale and bargaining power of one party over another. Kickstarter is a 100-ish headcount company located in Brooklyn, NY. This is hardly a captive employee pool compared to say, factory workers in a small town whose entire economy is centered around that one factory.
If Kickstarter workers unionize, I don't not believe it will results in two sides with equal bargaining power, Kickstarter will be in a substantially weaker position. If Kickstarter refuses the offer, all function ceases. If the workers refuses the offer, they have the robust job market of Brooklyn NY to fall back on.