"Deep Throat" is a Fig Newyon of W&B's imagination. DT was concocted to divert attention from those that needed it and to add suspense and credibility to W&B's story. Ir was also the "hook" that got a lot of people to pay attention - those that otherwise wouldn't.
Any ol'convenient corpse can be Deep Throat. This was probably cooked up when Johnny carson died.
I agree that there never was an actual Deep Throat.
In fact, reflecting on the Rathergate episode, I'm even more convinced that the fake memos were the same ploy that W&B used in making up a source for news they "knew" was true.
Unless the actual DT comes forward before his "death", I will never believe he existed.
G.Gordon Liddy has often said that Woodward has no real DT, and will, after the death of some suitable nominee (GHWB, Haig, Kissinger, etc.) that innocent dead person will be saddled with Woodward's DT identity.
Think about it: If it was you, why would you keep it secret if you knew Woodward would "out" you after your death? You would instead take measures to get your version of the events out there so your motives or actions are not misunderstood. You would not try to keep it secret unless you knew you could keep it secret forever--even long after you were dead.
Deep Throat never existed, and if blogging was around in '74, Woodward would have decided to retire a few months later just like Gunga Dan.
We will see.