I am someone who has believed that that there is a good chance that Osama Bin Laden has been dead for several years and that his #2 henchman, Ayman al Zawahiri (who always was the brains of the outfit anyway) has been running the organization for some time. It is obviously in Zawahiri's interest to make people believe that OBL is alive since OBL is the one who commands their love and loyalty. Audiotapes released over the years purporting to be from Bin Laden could have been faked from older audiotapes.
Now, I am not a terrorism expert and I have no inside information. My reasons are psychological. Let me explain.
1) I don't believe that someone like Bin Laden could go for so many years (he hasn't been seen on a NEW videotape since 9/11. He was apparently seen in Afghanistan briefly, but then completely disappeared from the radar for the last 2 years now) without having some videotape of himself made showing his followers that he was alive and well-- if for no other reason.
2) his own ego would demand to be the center of attention in all major terrorist matters. Just his name being bandied about would not be good enough (at least for this long), especially when secondary persons (al Zawahiri; al Zarqawi etc.) have numerous videotapes airing on al Jazeera and up on various internet sites glorifying terrorism.
3) We have seen his #2 guy twice in these last two years. Why use #2, when #1 will rally the troops even more?
4) Surely he would realize the value to his adherents to be able to see him and give him the adulation he desires and they are desperate to give?
Granted that the videotape of Zawahiri released today might be the "signal" to initiate new attacks here in the U.S. or elsewhere, but why not have OBL do it himself?
1) he's so close to being caught its too dangerous to make a videotape of him
2) he's so ill that he is completely unable to star in his own videotape
3) he's dead
I happen to like the third reason the best. Hey, I can hope, can't I?