How do unions operate when anyone with a pulse can walk in and do your job? This is a serious question. Particularly with the Apple store, where associates exist basically to fetch items from storage. It pertains to grocery workers too; a large portion of grocery baggers in the US are unionized. How do the unions bargain with capital in this situation? Warehouse workers are different; that is certainly semi-skilled labor, and a strike could be ruinous to your business. But there is zero barrier to entry for retail.
It's generally accepted that unionizing retail staff and other short-tenured labor (i.e., workers don't stay at the job for long periods of time) is very difficult.
When I worked jobs with similar functions, the idea of expending effort organizing and agitating when I planned on being gone after a year would have been ludicrous. Unionizing is generally a short-term loss for workers under the hope for a long term gain.
As for whether or not the union can hold if scabs can be brought in...not generally. They can unionize, but their main source of power (withholding labor) is greatly muted. Even industrial unions, where time to productivity is probably higher, generally have to discourage (even at times to the point of violence) scabs during periods of heavy labor militancy.
Costco employees are unionized. They are also insanely fast and very good. You cannot hire someone with those skills off the street, and the Costco wage scale reflects that -- a 5th year employee can easily earn double what an entry level worker makes.
That wage scale is carefully negotiated between the union and the company to divide the value created by lower labor turnover and increased specialization/experience. The cost of the union is relatively low compared to the value created by having well-trained workers. It is likely that equally skilled workers could attain the same (or better) pay working for an equally enlightened corporation, but that would be a rather unstable setup.
There's a cost of acquiring and training staff – the nuance of performing any job takes time and effort to learn.
Hiring a few new employees and training them is easy for an employer to do, but being forced to suddenly rehire your entire workforce is daunting. Any business would suffer dramatically if forced into this situation.
