Those in govt, and without, who were quick to dismiss terrorism as a cause of this tragedy should think about the possibility of someone interferring with the telemetry and data links to the shuttle.
A long time ago I had a discussion with a gentleman who was involved in the early shuttle computer systems and telemetry setups. He indicated that there were ways to purposely interfere with data transmissions just like someone can hack a computer over the internet. Not very easy to do, but absolutely possible. I'm trying to find this guy so that I can see if he still feels this way.
With so many people and so many firms involved with various aspects of the computer systems on the shuttle, it would not entirely surprise me if it is found that the shuttle computer software, and/or the data links were compromised.
The angle of attack and direction are very critical for re-entry into the atmosphere, and it would only take a momentary glitch to cause the catastrophe seen in Columbia.