I can't fathom a tire going out of balance as it wears, short of locking it in a long slide. If the cosmetics bother you, I can see the purpose there. For what it's worth, I don't have any problem with them. Just never understood what the appeal was. Thanks for clarifying that.
It's the same concept as they point out on cars with their "lifetime balaning" guarantees. Sometimes, albeit rare, a tire can wear unevenly (especially if you don't pay careful attention to air pressure, which is a MUST when using only two wheels). Also, bumps and/or vibration, or constant centrifugal force can sometimes cause you to send a balancing weight flying (happened to me just this weekend).
Although all of these issues aren't the norm, they become more important when you rely on two tires instead of four. I never even considered balancing beads until this weekend, when I rode a couple miles home with a thrown weight in hand and a slight wobble to the bike.
I consider myself lucky that I saw the weight fly off around the corner, and even luckier when I was able to find it! Even LUCKIER that I was within 2 miles from home after a long trek through the lovely countryside of Oklahoma!
Ok, ok... after all that long story, I too can see the value of balancing beads now, and will be switching to them, as opposed to the traditional weights, soon!