Lol apparently somebody purchased the domain bostonmarathonconspiracies.com and the message on the website reads:

"I BOUGHT THIS DOMAIN TO KEEP SOME CONSPIRACY THEORY KOOK FROM OWNING IT.
PLEASE KEEP THE VICTIMS OF THIS EVENT AND THEIR FAMILIES IN YOUR THOUGHTS.

THANK YOU"

http://www.huffingtonpost.com/2013/04/16/boston-marathon-conspiracy-theory-website_n_3093105.html.

First of all, no. Secondly, even if it was then what does it prove?

From the Youtube video. 2:27 to 2:32. The blood and gore is gone when the man passes infront of it.

Why ask me what does it prove? All I said was nice find. I don't need to explain that. make your own conclusion when you see it.

Watch it in fullscreen. It's a blood-soaked towel being pulled away from someone off camera. At least, that is what it appears to be from my perspective. 

it might be a flag or a towel, or just the blood disappearing.  I don't know man. lol

Oh dear sweet lord! We have conspiracy theorists about this one? For what purpose, pressure cookers need to be banned so they needed an excuse? For God's sake, it's in the middle of Boston at a huge event, why would anything be faked, and how would they make all those people believe it? I have personal friends that were nearby and can tell you that there's no fakery needed. Looks like a bloody towel that somebody off camera grabbed while the shot was blocked, you're bound to find some kind of strange illusion in hours of live feed.

I dont think the physics work out there lol. If that was the bomb how is the mailbox unharmed and the railing bend towards it?

the mailbox is bolted to the ground and not moving, the railing is just resting on the ground easy to move. I agree it looks odd how the railing is positioned, but perhaps bystander fleeing the bomb moved it like that.

Even with it bolted it should still show damage. Also someone running away towards the explosion doesn't make sense. Also fbi said it was a dark colored backpack or duffle bag