I think the yo-yo's were discontinued because although they looked nice, they were suspect to breaking. For instance, the bit that goes into the side of the iBook can fray easily as the wire gets bent back and forth over time and repeated use. Some people have reported shorting and the cabling going black. An interesting side note is that you know how the power port on the side of the iBook glows amber whilst its being charged and then turns green when its full? well originally Apple wanted the entire yo-yo adapter to glow colours like this. I've been fortunate with my yo-yo and its worked fine over the last three years but I was aware of the adapter shortcomings before I got my iBook, otherwise I probably would have treated it more casually. Now I think the difference between the yo-yo and the white brick adaptor is that their plugs that are inserted into the iBook are different sizes. If you have one of the first revision of white Icebooks, then you can probably use the yo-yo quite happily, but if you have the 600MHz onwards, then they use a different socket size.