There was a flurry of speculation at the weekend that Osama bin Laden may have died. Other reports over the past few years have proclaimed the al-Qaida leader to be dead or at least seriously ill.

Governments around the world, from Washington to Islamabad, are sceptical about the tale - as are specialist bloggers such as Juan Cole and Marc Lynch. Meanwhile, the Asia Times reports that Bin Laden has recovered from kidney trouble and has been travelling between Pakistan and Afghanistan "in a double-cabin truck with a few armed guards". Take your pick.

For the more conspiratorially-minded, the story about his death may have been planted by western intelligence in the hope that he will have to prove he is still alive by making another video - and perhaps giving clues as to his whereabouts in the process. Not that any of the previous videos have been much help in that. Equally, some suggest, it could have been planted by al-Qaida to persuade western intelligence agencies there is no point in continuing to search for him.

Fascinating though it may be to speculate about Bin Laden, I doubt that it really matters now whether he is dead or alive. Even from al-Qaida's standpoint he has probably outlived his usefulness and in an Associated Press report today, experts suggest he has little or no operational control over far-flung terror cells.

It is also dangerous to assume that capturing or killing him would have much effect on the level or terrorism overall. Look what happened with the killing of Abu Musab Zarqawi in Iraq. Despite the American jubilation, the effect on the ground was negligible.

In the five years since the September 11 attacks, the nature of the problem has also changed, as a recent report from Chatham House points out. The threat from al-Qaida itself has probably diminished as the threat from other extremists has become more complex and harder to combat.