I am indebted to Zaria for this piece of info, although it supports the official view rather than the conspiracy. She urged me to input 'Boston Bomb Conspiracy' into YouTube and i did. The first item up was this:
http://www.youtube.com/watch?v=ENd3q9bgbvI&bpctr=1367438191
(If the link doesn't work, input the same search term and hopefully it will come up first - it has an extra layer of protection on the link.)
For those of you who are still hanging onto the Craft International story, it definitively identifies the men as members of the Massachusetts malitia who were assisting with the security on the day. The video shows pics of the individuals concerned - they are not Craft. They can be seen helping in the aftermath of the bomb. The guy who was supposed to have left a backpack can be seen with his backpack still in place, after the blast.
Secondly, it shows another photo just before the bomb with Dzkokhar standing a few feet behind a number of the known victims - including the 8 year old boy who was killed. It places him unquestionably right at the key spot (about 1min 20 in the video).
Dzhokhar was right there, in the right spot.