Five yesterday, three today. Surge + Mahdi Army cease-fire + Sunni Awakening Councils = fewer attacks on US forces = increased foot patrols = fostering goodwill among Iraqi civilians ==> we win.
Unfortunately, increased meet 'n' greet foot patrols = increased opportunities for direct attacks on unarmored soldiers ==> get back in those up-armored HMMVs, boys ==> so much for that hearts and minds thing.
It's a vicious circle. If the soldiers don't engage civilians in these community relations-styled patrols, they'll continue to be viewed as distant, brutal occupiers looking for their next target from behind mirrored shades. But when they get out of their vehicles to chat up the locals and display their rebuilding-Iraq human side, they're terribly vulnerable to suicidal maniacs in explosive pajamas. Which will have the additional repercussion of making the men in the foot patrols even jumpier than they already are, which is going to lead to more indiscriminant targeting after--or, even worse--before an attack happens. More collateral casualties breeds more distrust and outright hatred among the civilians, and that brings more attacks, and that makes more guys more inclined to grease anyone who looks at him crosseyed, and that wins the insurgents more sympathizers, and that...
You get the picture.
It doesn't matter at this point if the attacks are being carried out by the one disgruntled Shia or Sunni or AQ operative or rogue Iranian Revolutionary Guard in a crowd of 100 people. Remember the one kid back in sixth grade gym class who kept fucking around, leading the coach to punish the entire class with 45 minutes of running laps (yes, Tom Roper, I'm talking to you)? Same deal. It only takes one suicide bomber mingling with a foot patrol to make every surviving guy in the unit deeply suspicious of every Iraqi on foot with bulky outerwear he will ever see again for the rest of his tour, whether that Iraqi is a man or a woman or a kid, make it a no-brainer for him to err on the side of caution, where "caution" here means not hesitating to pull his trigger on anyone who crosses his new, significantly lowered threat threshold. And it only takes one US soldier blowing away a woman who turns out to be carrying a bag of vegetables instead of bombs to turn every surviving member of her family into confirmed insurgents.
And so it goes.