"We control the horizontal. We control the vertical." Whatever the truth is regarding the NSA story, we may never know it. What we can discern, based upon what we have been told, is that IF what we have been told were actually true, the Government could have used the "Person of Interest" tool PRISM to stop the Boston marathon bombers. They didn't. So either they knew about it and chose to do nothing, or they didn't know about it. I would tend to believe the latter.
As for Trayvon Martin, remember that photos don't tell us who was the good guy or who was the bad guy, but in my opinion, a media-photoshopped image counterbalances a thousand words.
Pictures and text from Trayvon Martin's mobile phone can be viewed here. Above all, we must remember that prejudicial opinions passed off as facts will never pass muster.