Google's Android mobile operating system is suffering (or thriving, depending on who you ask) from a glut of customised versions. Knowing which apps will run on which phones and whether yours will behave correctly (or whether your phone company has accidentally or maliciously crippled it) is like rolling the dice. You never quite know. I think the nintendo DS is being eroded a little by the many different versions. We are also starting down a similar path with point of sale systems. Right now there are three competing systems in Australia: magnetic stripe, chip-and-pin, and RFID. It's not so much a problem for consumers yet, but I can imagine businesses being annoyed at the competing systems and the constant upgrade treadmill.
Platform stability is important for consumers. You want to know that what you buy today will be supported tomorrow, and that it's not a waste of time and money to invest in it. We have Betamax anxiety about every new consumer technology, especially when backwards compatibility is seen as a stifling restriction on progress.
Mokalus of Borg
PS - Blu-Ray is still suffering from this.
PPS - Despite winning out against HD-DVD.