I'm not a big fan of George Soros, but this piece on the War on Terror is pretty reasonable, in my opinion.
Let me restate Soros' four objections in my own words:
(1) When fighting on their own turf, terrorists are essentially guerillas. So you wind up with the major problem that plagues anti-guerilla warfare: how to stop the guerillas without turning the populace in which they live against you (which, unless you decide to stop potential future guerillas by wiping out or severely and permanently tyrannizing the populace, is the main goal of the anti-guerilla's strategy; wherezas the strategy of the guerillas is to make it that you alienate the population so that they will support the guerilla forces).
(2) There is no single terrorist organization that we can go to war with, and not all terrorists threaten us or are part of the same threat. We need to view terrorism as a bunch of different problems, not lumpable together into one big problem (except to the extent that we look at the law enforcement side, where we can develop general rules to catch terrorists and to stop terrorist attacks). There is also the nasty side of "one man's terrorist is another man's freedom fighter." The War on Terrorism can be used to suppress dissidents by labeling them "terrorists." I'm not saying that we would do this, but the War on Terror could give less free countries cover to do so.
(3) We are fighting mosquitoes with an elephant gun.
(4) We need to be careful to look at how we appear to the rest of the world, and to determine when we are right and they are wrong, and when perhaps their perceptions are justified. We also have to consider when, even if we are right, discretion is the better part of valor.
That is all.