As a pilot, former engineer and now an Air Traffic Controller here is my 2 cents.
I believe that any pilot complaining about the decision to close airspace has his right to his opinion. He does not pay maintence bills and in all likely hood has no idea of the cost of maintence and the actual threat that volcanic ash poses to the components of an engine. There is enough evidence shown on this thread of the immediate results of ash ingestion to a gas turbine engine, e.g the finnish airforce f18 photos on page 31 or so.
From an ATC perspective, the law states that we may not clear an IFR aircraft to operate in an area known to be affected or forecast to be effected by volcanic ash. So why is there an argument here about the decision that was made to close airspace?
Personally I believe any pilot willing to fly in such conditions carrying passengers is irresponsible and this industry has no place for such people.
The economic effects of this volcano are dire, but nothing compared to what would happen when a few airliners crash because of it.