It still surprises me that this topic inspires such interest. But--so be it!
Stance-width is a purely functional consideration. Different functions will require different stance widths, same as any other activity we do. Watch any sport of motion--hockey, tennis, football, boxing, martial arts, gymnastics, almost ANYTHING--the athletes will use everything from feet together to feet way apart, as needed. And, for some odd reason, in most of those sports, people rarely even think about the width of their stance--they just let it be "natural"--as it should be.
Of course, if looking a particular way is important to someone, then this "look" takes on a function. If that "look" on skis is to have the feet clamped together, then by all means clamp them together! Practice it, and you will get good at it. But realize the other functional limitations that accompany this stance.
Stance width has implications for balance, edging, and steering (rotary movements), in particular. As Jonathan says, "too close" is, by definition, a problem. But what is too close?
The feet MUST be able to move independently, otherwise our movement options become severely limited. When the feet rotate about one pivot point, instead of two, it is impossible to steer the skis precisely into and through a turn. With a little separation, each foot can provide the support against which the other turns, freeing the upper body to do other things--like balance. While we've discussed this point in greater detail previously here at EpicSki, suffice it to say that, if you can't turn your legs independently of each other, then you can't turn your legs at all! All you can do is turn your entire lower body, including your pelvis, against your upper body.
Your stance is "too close" too whenever one ski or leg interferes with the other. Again, this can be an edging problem, a rotary problem, or both.
The most important point, I believe, is to remember that, even though many expert skiers ski with apparently narrower stances than beginners, regardless of stance width, a carved (or partly carved) turn, balanced on the outside ski, REQUIRES that the skis be pulled APART--the inside ski tip MUST be pulled away from the outside tip, into the turn, or it will interfere with the outside ski's ability to carve. It need not be pulled FAR apart, but the moment the activity of the inside ski stops, so does the carve. (The exception to pulling the inside ski into the turn occurs when both skis are weighted, and both skis carve into the turn. But even here, SOMETHING must provide a force to move that inside ski into the turn--away from the outside ski. Whether it is the snow pushing it into the turn, or the inside leg pulling the ski into the turn, it is the opposite of what happens when the skier pulls the skis together!
If TYING the feet together would be a handicap, then forcing them together any other way is equally so!