You may be confusing your neighborhood "fortune teller" with prophets.
Once again, David Wilkerson is not a prophet, so we're not talking about him.
Prophets (of God) in the Old Testment only speak what God gives them to speak. No more, no less. If they lied, they died (stoning).
I understand how you feel. I guess we all just want someone to tell us what we have to do to make it better. Just as long as he's not a Christian preacher. Right?
"Word of the Lord," prophecies, fortune telling...I'm still waiting for Pat Robertson's catastrophic revelations that were supposed to happen in 2006, then 2007. Many a Christian preacher has gotten a bit of fame and morphed into an attention whore.
I trust my Bible and a few men of the faith who have proved to be reliable - as the Scriptures direct. Anyone who says God told him that bad things are going to happen either lives under a rock or wants attention.