It's possible that increased activity has allowed them to reestablish their influence in a lot of areas, particularly along the Pakistani frontier, since they can pitch even their defeats as victories to the largely illiterate tribesmen from whom they recruit.
It's also possible that they're trying to wage a war of attrition. Most analysts, right as well as left, civilian as well as military, believe the Taliban is trying to raise the Coalition casualty count to the point where Europeans, who are so sensitive about their soldiers getting killed, will decide on a withdrawal. But despite some reservations, the current rate of deaths doesn't seem likely to do that.
The Taliban may be hoping that, even though they incur seriously heavy casualties, if they can, in just one battle, inflict really heavy loses on Coalition troops (wipe out a platoon, perhaps), they might be able to trigger the withdrawal of some of the NATO contingents. But doing that might cost the Taliban hundreds of more dead followers.
Piling up the number of casualties may actually serve as a recruiting tool, since it may attract recruits seeking to avenge the deaths of kinsmen (a popular pass-time in the region) as well as many of the most ardent among the faithful who want to seek martyrdom themselves. But how long can they keep this up? Sooner or later the pool of volunteers is going to dry up. American and NATO intelligence officers are readying informer networks that will report on what the "chatter" is, over the Winter, in pro-Taliban areas. Considering the heavy losses the Taliban took this year, are their supporters eager for another round in 2007, or are they dismayed and discouraged? There may be enough chatter to analyze, by the end of the year, to form some conclusions.
In Afghanistan, government officials, tribal leaders and NATO generals are trying to makes sense of the seemingly suicidal, and pointless, Taliban tactics. For the last six months, the Taliban has been conducting a lot of raids, ambushes, and suicide attacks. This is reasonable for an irregular force. But they've also been carrying out a lot of operations that involve larger forces (e.g., on platoon, company, and occasionally higher scale). Moreover, these troops don't "melt away" as soon as Coalition/Government troops turn on the heat, but fight back. They Taliban tend to lose these stand-up fights, and they don't inflict very many casualties. In fact, the Taliban have been losing 10-20 men for every NATO or Afghan soldiers they kill. Even by Afghan standards, this appears insane. So what are they up to?