I think Walt was special the same way Desmond was special. I think the others (Jacob) were interested in him because at that point, Jacob didn't know who is "failsafe key" was. The way in which birds flocked to Walt and end up dying around him indicates he could have had some abnormal electromagnetic outputs; signals that would attract the birds, and ultimately, confuse and destroy them.
The one thing I always thought was being ever so hinted at throughout the show.... something I always loved to view as truth... AND something I wished the show had done (AND something that would have been such a great way for them to solve the problem they had with aging Malcom David Kelly) was that Matthew Abaddon was Walt.
Now that we've seen the epilogue, we know that Walt goes back to the Island with Hurley and Ben. Who's to say Walt does not grow up on the Island with Hurley and Ben an grow up to be Matthew Abaddon (Matthew Abaddon is to Walt as Jeremy Bentham is to John Locke) and with the islands history of Time Travel, travels back in time per Hurley's instructions and interacts with the Oceanic Six and Locke. Think about that watching the scene between Hurley and Abaddon. ESPECIALLY the scene between Locke and Abaddon when he's pushing him down the hallway in the hospital. It also adds an interesting point to Locke and Abaddon's seemingly pointless visit to Walt. I wish this had panned out. Not like a full on "I'm Walt" moment from Abaddon... but imagine if while sitting in the car at the cemetery with Locke, Locke had asked him something while frustrated. Like who are you? How do you know yadda yadda yadda..... Abaddon could smile knowingly at Locke and say "Can you keep a secret...?" And as Locke looks at him puzzled... BANG... Abaddon is shot...
Regardless, I still like to think of Abaddon as Walt. Thoughts?