I think JoKenna is speaking about the "herding" or "lemming" mentality of many WDW guests. Often times, guests just seem to follow other guests rather mindlessly and fall in line without sizing up the situations first.
At the various park entrances, for example, the ticket machines will always accommodate two lines. Yet, I often observe many guests (20, 30 or 40 at a time) lined up single file behind one another while the "other" side of the ticket machine has no one in line. Naturally, I head for the "other" side.
Same thing is true at the various counter service food locations. The CM at the register always works two lines, yet often guests will mindlessly stand on one side only and not use the "other" side. I always head for the "other" side.
Same thing is true of the lines for the various attractions, going through the multiple doors entering attractions, getting fastpasses and using the WDW transportation system. Lots of guests tend to herd (i.e. follow others).
As Jokenna correctly points out, if you can think quickly and adapt to the various situations as they develop, you can cut time in line, get the best seats, get around property faster and generally avoid "deadheads" that might otherwise impede your WDW experience.