Does Widmore need to find the island for his own failing health?
There's been some blog speculation as to whether the true reason that Wid needs to find the island is because he is desperate to get healed of some fatal malady. Perhaps that's why he doesn't sleep at night -- because he's dying, and the fear of life's deadline looming closer every minute is pressing in on him. There may be very little time left for Widmore to find the island, which could explain why he pulled out all the stops and engaged the freelance militia to cut a swath to the healing source that he needs so badly before it's too late.
That makes some sense to me. I really could not understand why he'd contract a team of mercs to eliminate all the interference, just so he could be the first to open the Fountain of Youth Adventure Park on the island. Granted, it would make him the richest man in the universe, but I got the impression that he's almost at that apex anyway. And if he is dying, it makes Ben seem all the more cold-hearted, as he stands in Widmore's bedroom mocking a dying man's sleepless nights, when he has the keys to Wid's recovery in his hand so to speak. After what Ben said to Locke in the Orchid, you can almost image the conversation as Widmore says, "Ben, you know that I'm dying." And Ben replies with, "So?"