My theory is that news of attacks are being suppressed to interrupt the goal of the terrorists - which is to amplify the effect of an otherwise puny attack through our mass media, and mass hysteria. It seems to be a reasonable policy to me, even though I'd like to know the facts, if those facts caused the masses to misapprehend the actual risks of air travel, going to the mall, working in an office building, participating in the stock market, etc., I'll do without.
I think that it is good policy to interrupt the terrorists' intent.