"Trusting DialIdol is lot like trusting exit polls."
That's a good point...although they're a bit better because with exit polls you have to take the liberal bias of the media into consideration.
I think that DI will have continue to track close to the show's results. It's a sampling of voters that while uncontrolled scientifically, still manages to give you an idea of who the lowest voter getters were.
Note that AI has not always said who the lowest two vote getters are each week.