I like this idea ... and already have a ton of that tubing (we use it in our business). I currently use the little fuzzy pony tail holders but they don't wrap as tight, stretch eventually, and you can't see through them. My husband always has some off-cuts of the clear plastic tubing so I'm going dumpster diving at our shop tomorrow!!
Gosh ... I can even use a sharpie to write the thread weight on them so I don't grab a 60wt when I wanted a 50wt!!