CORRECTION TO MY PRIOR POST:
The VA definition of "terrorism" DOES (contrary to my prior understanding) seem to require that the prosecution somehow prove that an accused commit his acts with the intent to "intimidate" the civilian population OR to "influence" by intimidation the conduct of the government.
§ 18.2-46.4. Definitions.
As used in this article unless the context requires otherwise or it is otherwise provided:
"Act of terrorism" means an act of violence as defined in clause (i) of subdivision A of § 19.2-297.1 committed with the intent to (i) intimidate the civilian population at large; or (ii) influence the conduct or activities of the government of the United States, a state or locality through intimidation. * * * *
I have no idea how the VA prosecutor was able to argue that the DC Sniper's intent was to somehow coerce the government if there were no demands made. It MIGHT be that VA went strictly by the (i) portion of the definition: that Mohammed's and Malvo's actions were intended merely to intimidate the civilian population at large. If so, their definition of "terrorism" is pretty meaningless. ANY acts consisting of a crime spree might fit within such a loose definition.
The problem with your definition of terrorism - which requires demands made on a government - is that it is too restrictive. Most commonly accepted definitions of "terrorism don't include that. I believe it would exclude 9/11 as a terrorist action, would it not - as no specific demands were made to the government were they? Hasan's "demands" are, as you said - vague - to vague to be considered a threat much less an actionable threat. In fact, the only potential of "threat" is in hindsight. The Anthrax killers notes while they did not include a demand did contain a definitive threat in wording. I think what is happening here is that there is a semantic hair-splitting going on in an attempt to make Bush's watch look "clean" and Obama's watch look "dirty".
I would at this point call Hasan, Anthrax man, and the Beltway Sniper terrorist actions because the intent was to intimidate civilian populations. Their demands and rationale may not have been clear but at least for Anthrax and Hasan, it wasn't just a pissed off guy going postal - there was methodical preparation and intent.