Service Challenges at McDonald's: Did Success Breed Problems?

The Wall Street Journal reports that McDonald's has launched an initiative to improve customer service.  Apparently, the company has recognized some significant problems in recent quarters.  Here is an excerpt from the article:

In a webcast McDonald's executives held with franchise owners last month, the company said 1 in 5 customer complaints are related to friendliness issues "and it's increasing," according to a slide from the presentation reviewed by The Wall Street Journal. The webcast identified the top complaint as "rude or unprofessional employees."  One slide said that complaints about speed of service "have increased significantly over the past six months." Another mentioned that customers find service "chaotic."  "Service is broken," said a slide from part of the webcast delivered by Steve Levigne, vice president of business research for McDonald's USA.

What could be causing the problems at McDonald's?  I have several theories.  First, the company has experienced many consecutive years of same-store sales growth.  The firm prospered during the struggling economy, as folks looked for value.   Moreover, McDonald's foray into coffee drinks turned into a blockbuster success.   One wonders if the growth simply began to tax many of its smaller restaurants.  Did crowds overwhelm the firm's processes and systems?  Second, McDonald's did expand its menu to offer more drinks as well as healthier food options.  Did the new options add so much complexity that they slowed down service considerably, or made it difficult for employees to provide food in an efficient manner?  In short, I wonder if success brought these problems upon McDonald's.  Perhaps there is a lesson there for every rapidly growing quick-service or fast-food restaurant chain.   Growth may be wonderful, but service deteriorates, you may have a major problem on your hands.