Kirk McElhearn over at Macworld has an excellent piece summarizing the ways Apple IDs present all kinds of headaches and troubles for their users. It's nothing others haven't said before, indeed -- we've written about it many times on TUAW, but the issue is so important, it's worth repeating as often as possible: the current implementation of Apple IDs suck.
Almost anyone with an Apple ID has an Apple ID horror story. They began when Apple unleashed its dotmac email service, then iTunes IDs, the failed MobileMe service and now its so-so iCloud service. All of those services could have one or multiple Apple IDs. Some IDs could belong to a single user, or some users could have an Apple ID that is an email they don't use anymore. And that's just the start of the problems.
In his article, McElhearn lays out the three most common scenarios users get into a jam with regarding their Apple IDs. It's an article everyone should read. And by "everyone," I mean, "Apple." And after they read it, they should fix the Apple ID mess soon, because in its current state, Apple IDs aren't going to get any easier to manage.