I think there's another factor to consider with the Realms novels: how many non-gamers read Realms novels?
When the Realms first came out, it was hot on the heals of Dragonlance, which was selling novels left and right(as the New York Times Best-Seller list attests, and since the PHB has never had that honor, somebody in the non-gaming community was buying those babies). Hence, when the setting came out, they also had a major trilogy of novels ready to go. Did many people read the novels, much like they may have read the Dragonlance trilogies, but not play the game associated with them?
Now, here's another question: were the novels always meant to have such an impact on the game setting? Here's why I ask- the first trilogy was set in the Moonshae Isles. Never heard of the place? Or, never heard of it until recently when the trilogy was re-released? Unless you were a hard-core FR follower from back in the day, wouldn't surprise me. It was almost as if the setting was transplanted from somewhere else- it even had different gods (Baal and Chauntea were "interloper deities" from the mainland). Very little changed there in all the transitions between editions.
Also, think of these characters: Alias, Danilo Thann, Giogi Wyvernspur, the Saurials, Cadderly. All of these drove some serious novel sales, but not a one involved in an RSE. Even Elminster's first novel appearance was in a one-shot story- "Spellfire." All their stories took place in isolated situations, much like any other adventure.
So, would it be safe to say that the original philosophy of the novels was not to affect the game, unlike Dragonlance, where the novels very much defined the game? When did this change? When one major event story sold huge? And if it did sell huge, was it selling as much to non-gamers as gamers? Is that still true today?
If the sales of novels are what's driving the whole line, then I think the Eberron people have the right idea: keep the novels out of the main setting.