The FBI (or Homeland Security) were informed by another country (Russia?) that the suspect #1 may be radicalized. The US looked into it and thought that there wasn't enough to put him on their watch list (even though he had already made some radical you tube videos). This is all well and good. It is America after all.

My beef: don't you think that once the explosion occurred a memo would have been sent to all local agents to review all Boston area cases, even closed cases. Wouldn't you think that whoever worked the original case (and who went to subject 1's home for an interview) might have looked at the video and said "whoa! I went to that guy's home 2 years ago!!!!!" Even though they closed the case, wasn't there a photo!!!!!!!!!!!!!!!!!!

If subject 1 was identified before they went public, both could have been picked up neat and clean. Heck, subject 2 was partying 2 days after the explosion.