If Dave Hart is expected to call a presser and address the situation everytime a rabid fanbase wants to run with a fabricated story he would never get anything done. The fact that fans wanted to believe "It's Done" and "Soon" from some storytellers in Gruden thread #1943 it's their own fault. Dave Hart had nothing to do with that.
Dave Hart absolutely cannot call a press conference in each situation you reference above. However, many times the situation "gets away from you" if you will in things as public as this. A recent example would be President Obama's endorsement of gay marriage. In no way shape or form do I believe he intended to do that as quickly as he did--too many culturally red states like Ohio, Florida, North Carolina, and Virginia were in play. He was forced to move in that direction by the fuel that is Joe Biden, speaking freely on Meet the Press. Joe Biden was an agent of the President and it forced his hand.
Similarly, in this situation, we clearly have a person or people who are feeding various individuals in the media with information that each of them has deemed credible (ex. Chattanooga v. Knoxville media). Each in essence are acting in the same way as Joe Biden--agents of the university because they are "players, soon to be coaches, boosters, athletic department officials, etc.)
The two examples diverge in how President Obama handled his predicament.
Obama knew his base was heavily in favor of it, any equivocating or non-answers would infuriate them--he knew that, so he immediately cut losses and endorsed same sex marriage consequences be damned.
In our example, the combination of no information in the form of leaks from sources around the University, the hunger of this fan base, and too many contradictory Gruden stories coming from the media (i.e. Chattanooga) and you've created a wildfire of speculation and anticipation. It has steadily been growing all week reaching the crescendo it did today, because Dave Hart, the central figure of this search, did not bothered to put it out.
I'm on twitter like many of you. I follow many of the national and regional sportswriters. Our drama has been the punch line all afternoon. We look like a joke. As an alum I am embarrassed by the donors would couldn't keep their mouth shut and the Athletic Department that refused to acknowledge reality and forthcoming PR mess they are partially responsible for.