Too many innocent people are getting caught up in the crowd-sourcing thing. See my comment here as well as this Page regarding the same guy (an American high school kid of Moroccan descent).
I knew this photo of the two “possible suspects” in khaki were going to come up as I saw the image the other day, so I saved a link to a photo showing that it can’t be them because there’s a photo of them post-blast on the scene with their backpacks intact. That fact gets noted almost nowhere.
It can be verified by downloading the full-size original version provided by the photographer, hahatango, on Flickr. Let’s take a look:
1.) Here’s the default image from Flickr showing the full post-explosion scene. I’ve circled the “khaki pants guys” in bright green.
2.) Here are the same guys, taken from the full- size version of the photo at 100% magnification, with everything else cropped out. It’s them.
Still not sure?
3.) Same guys, same full-size photo, this time at 300% magnification. No, you can’t see their faces, but if you’ve looked at the numerous other shots of them where their faces aren’t blurred out, there’s little doubt it’s them.