Sure that's one scenario, but the fact is lipo cells are like a finger print, no 2 are identical, and they can vary in charging/discharging characteristics, especially on cheaply made packs. This has nothing to do with one cell being bad, just slightly different. After numerous cycles the difference adds up to an unbalanced pack. If you've been in rc long, you are aware of the practice of balancing NiCad and NMHi cells, and/or using "matched" cells. It's the same concept. Try using a cheap ebay lipo for a year or two without balancing it and let me know what happens.