By Noble prize winning economist Paul Krugman : http://www.nytimes.com/2009/01/19/opinion/19krugman.html. Most certainly worth a read.
By the way, speculators most probably play a leading role in the second round of the banking crisis which appears to be underway right now.
Theft is a crime. In a couple of days a speculator can "earn" more money than a thieve can steal in a lifetime. Of course, as speculators are free market regulators (yeah, right !) or at least free market actors, and as free markets are sacred, all that is perfectly legal ; we cannot call them thieves and their "job" cannot be called stealing.
And why not ? In my own book, speculation (i.e. earning indecent amounts of money without a decent amount of work) should be considered a criminal activity. At the very least it should be called legal theft.
Mmmm ... my definition of speculation is not quite airtight. It would cover a lot of businessmen too. But wouldn't that be just, even if it's not justice in the legal sense of the word ?