The obvious question would be "why should there be a limit?" The story doesn't answer that question. In fact, it doesn't even ask it. The closest they get is to suggest that dispensaries are too close to homes. I wonder if they feel the same way about alcohol sales. It is also suggested that many of the dispensaries are operating illegally, selling over-the-counter instead of by prescription only. I think marijuana should be available over-the-counter, but even if one believes that it shouldn't, the solution is to enforce the existing law, not arbitrarily limit the number of dispensaries.
As an advocate of medical marijuana points out in the story, driving sellers out of business is going to increase the black market in marijuana, with all its unpleasant effects. So given all this, why would one want to eliminate sellers of medical marijuana? Who are the "some" people that I mentioned in the second sentence of this entry? Here's a possibility: The first person interviewed in the story is the owner of a medical marijuana dispensary. Is this a classic case of the baptists and the bootleggers?