It's been an ongoing problem for years now for a lot of people, but it never affected me until tonight - Apple really, really, really needs to find a way to merge iCloud accounts.
I was attempting to watch a movie I bought on iTunes years ago when I got the "You Are Not Authorized To Play This File" warning. WTF? I did some digging and discovered this was bought with my old iTunes account. In the bygone era before iCloud, Apple offered a $99 a year service called .Mac. I subscribed all the way back in 2004. .Mac turned into MobileMe and eventually iCloud, when it became a free service. When it changed to iCloud I started a new account with my primary email address not realizing it would effectively cancel out the past 7 years of Apple purchases.
There are kludgy workarounds involving using separate accounts for iCloud services and iTunes purchases, but they're less than ideal. Especially when you're like me and you've spent hundreds of $'s with both accounts. Add in iTunes Match and Apple Music and it gets even more confusing.
It shouldn't be hard for a company with the resources of Apple to set up an easy way to combine multiple accounts. You get to pick which email address you want associated with it and all your purchased content, services and subscriptions are merged into a single sign on.
I've been working on an iOS 10 / OS X 10.12 wish list, but after tonight this has gone all the way to #1.