Too many roads lead to Hurley -
1. The numbers, Hurley is the only one who is directly tied too all of the numbers from the mental hospital.
2. Libby was also at the mental hospital with Hurley and then shows up on the tail section crash site.
3. Did the MIB show up as Dave in the episode from Season 2: "Dave" to get Hurley to kill himself by jumping off of the cliff and did Jacob make sure that Libby was on the island get convince Hurley to not jump?
4. Hurley see's dead people - not with an island-acquired ability like Miles obtained from being a child on the island (perhaps that is why children are so important on the island - they easily acquire abilities from the natural electro-magnetic properties of the island)
5. Hurley is the only one who can see and talk with Jacob and as such has become the single most important of the candidates as Jacob has been directing Hurley since he died and appeared at the Swan site right after Jack & Co. returned to the present.