This is a somewhat ill-posed question, but I will try to frame it in a self-defense perspective. Disclaimer: I would consider myself an average marksman, not an expert by any means, but also an enthusiast in the limits of aspects of self-defense.
First of all, if we define the "effective range" of a pistol as the distance that can still injure a person, I have no reason to doubt the wiki entry. Of course, hitting the target is a strong function of experience and tools.
Generally, if the relative size of your front sight is reasonably smaller than or at worst, comparable to the size of your target, your sights are properly zeroed, you can hold the firearm sufficiently steady, and your action of pulling the trigger doesn't pull the sight away from the target, you have a good chance or hitting your target. This means that the longer the barrel, the more accurate you can be within reason. This is also a function of the burn time of the round inside the barrel, meaning that pistols, with their relatively short barrels won't typically achieve the maximum velocity and therefore range. I don't know if the amount of propellant in a 'typical' 9 mm round (for example) is matched to the burn time corresponding to the 'typical' barrel length? Perhaps someone can chime in about that?
Now, from a self-defense perspective, effective range is coupled with how you behave when you get an adrenaline dump, how your weapon is stored/holstered and drawn, and how practiced you are at these motions with different types of clothing, as well as other potential environmental factors. I can speak from experience at a range when I was first starting to shoot, that picking up the gun from the table in front of me and firing one shot as quickly as possible at a target -- even only ~10 feet away, at least half the shots completely missed the paper.
Talking with more experienced shooters (i.e. law enforcement, and "gun people") about effective distances with pistols, you essentially converge on a rough distance of ~20 yards (60 feet) - or the distance across a full volleyball court (lengthwise). Now, if you have the luxury of time in taking the shot, you can of course be much more accurate and precise at longer distances.
