While I suppose that's a remote possibility, I'd put it well down the list behind:
1. Al-Qaeda - (the usual suspects)
2. Norks - they've been feeling froggy lately, and today is Kim Il Sung's b-day.
3. IRA(?!?!?) - Double-bomb is their old MO, lots of Boston area ties, and the recent death of Thatcher may have made them long for the old days.
4. Anybody's guess is as good as any of the above at this point. False flags should never be discounted until they can be ruled out.
Right on the 4-hour mark of the marathon... was it on the hour, even? That might tend to suggest devices on a timer, rather than manually detonated.
Joe honey you forgot Yankees fans
PATRIOT Day, Tax Day, Heartbreak Hill, Marathon Race, North Korea 101st Birthday Celebration with bizarre threats, V for Vendetta and CNN OKC special on TV over weekend, bizarre articles on thisweek.com and yahoo, DeVrie University commercials with people with Red Socks on, Warren Buffett GEICO commercial with PATRIOT Paul REVERE on cell phone opening drapes saying British are coming,THEN FBI and State Police obtain search warrant to search apartment at 364 Ocean Ave., REVERE, MA. Must be just a “coincidence”.