Well, I was having a conversation with this friend today. We were discussing Halls of Origination, the tie-in with Ulduar and Algalon and then the Emerald Dream surfaced.
Let me put it this way:
What's the Emerald Dream? We know it's a "blueprint" of Azeroth. Someone might say a "back-up copy" of its original state.
Now, let's think about Algalon and the temple of Uldum. The Observer wanted to send Reply Code Omega, and activate the device. We prevented this at Ulduar. And later on, Deathwing wanted to gain control over it through Schnotzz (sp?). We prevented the armageddon once again thanks to Brann Bronzebeard.
Next point (apparently unrelated, but keep reading): Why is N'zoth corrupting the Emerald Dream? It does has it significance, granted. Ysera controls the flow of nature from this place and everything, but what if there's something more behind that?
Well, here's the interesting part. Since Deathwing (ergo, the Old Gods) wants to gain control over the Re-Origination device to reshape the world (someone might say, its original state. Maybe using a certain back-up copy to reinstall all the "data" into the world), you can relate that to the Nightmare's corruption. Corruption as in data corruption.
I don't want to elaborate much more on this, I just think that this makes sense. What do you think?