That article leaves a few things out...
1. You can use one icloud/apple account but register different emails addresses. Apple will verify the email and associate it in their database/dns with your device. Thus I have my iphone and ipad setup to one imessage account and my wife has her iphone and ipad sync'd. Same Apple Account different emails...
2. Now many people are getting that their email address (non apple) is already in use. This is most likely due to the fact that the email address was setup to use with their facetime on a Mac. Thus that unique email is syn'd with Apples DNS to that device, a Mac.
So In my case I have my primary email address linked to my iMac at home my primary work address to my Macbook Pro at the offfice...and then my icloud/mobile email linked to my iphone and ipad. In my wifes case she used her gmail to link up her ipad and iphone to imessage.
Much confusion here amoung my peers but I sorted this out late today. Works well. We could have gone with unique icloud accounts but that presents other issues covered by the author of that article...amoung other things.
Now the only issue with my system is the new Find my Friends feature as it only allows one icloud/mobile me per device. Thus a family sharing an Apple account is screwed but I'm sure this will be addressed down the road as that single family consists of a dad like me wanting to keep and eye on the kids...then again Apple may not like the shared system we all use...they would rather we all buy our own apps!