Well, that's not entirely accurate about the unionized public sector workers. They don't hand the money back themselves; rather, they have it taken from them by union officials who hand it back, with or without their consent. One of the big developments in Wisconsin was that when the state stopped withholding union dues from state employees' paychecks, a large fraction of the state employees—over half the ones represented by AFSCME, I believe—stopped paying dues. Which doesn't exactly strike me as evidence that the unions were serving their members.