Whitley left ZTK about six months ago. His choice, I understand.
The few successful paid programs were all ones who started doing it long before there were any dollars involved. Mike Wells, Larry Hungerford (Woodard & Company), Gib & John, early Computer Talk (Steve and Stephen, Deb & Gary), The Super Handyman (David Dalrymple) to name the most notable.
In those days, we invited those people to be true guest experts. They weren't paid, they didn't pay. Later, people like Mike Wells and Woodard & Company, Gib & John were all asked to buy a certain level of advertising to sustain their on-air presence.
More recently, the pay-for-play folks have been either mostly infomercial or so highly targeted they had little, if any, appeal to a general audience.
Frankly, I have always wondered how they got away without some sort of "paid program" disclaimer in recent years.