The Taliban say they have carried out their most successful "suicide shooter" attack so far, when an Islamic terrorist who managed to join the border police, turned his loaded assault rifle on American and Afghan trainers and killed six Americans on November 29th. This was the second such attack this year, in which nine foreign troops (including three British) were killed. There was one attack last year, and one in 2008. But it's also likely that few, or none, of these "suicide shooter" attacks was the result of Taliban action. The most recent shooter was a poor village kid, who had been in the border police for three years, and had, the day of the shooting, argued with his father (over persuading the son to marry an underage girl). The shooter was visibly angry after that meeting, and angry Afghans and guns are not a healthy combination.
These "suicide shooter" attacks are much harder to pull off than those using suicide bombers. That's because it's much easier to recruit and manage suicide bombers. Certain personality traits make someone very willing to carry out suicide attacks. And the chief characteristic is usually not fanaticism, but deference to authority and public opinion. This is one reason why Islamic terrorist propaganda glamorizing suicide bombers is so dangerous. Over a decade of this propaganda provides a large supply of potential suicide bombers, and even assists them in contacting terrorist groups to sign up. For terrorists unable to find these impressionable volunteers (who are easy to train and control), there is another pool of recruits. These are the deranged and impulsive. This is why you will occasionally hear about dead suicide bombers who were mental patients, or widows of terrorists. The widows are told, quite accurately, that they faced a dim future and that becoming a martyr for the cause was a good move. In these cases, the cash paid (by terrorist organizations) to the families of suicide bombers helped with the recruiting.
Terrorists consider suicide bombing a very effective weapon. But to make it work they need volunteers who are reliable and able to learn the techniques of getting to the target undetected, and then actually setting off the bomb. You don't hear much about it, but many (in some situations, over a third of) suicide bombers refuse to go through with it. Thus the many "handlers" that work closely with the suicide bomber, until the final moment. If a suicide bombing campaigns goes on for a while, only killing Moslem civilians, there will be a shortage of competent volunteers. All those dead Moslem civilians gives the attacks a bad reputation. That means fewer successful suicide bombing missions, and more captured (or surrendered) bombers, which results in more suicide bombing cells (and their hard to replace management and technical personnel) are destroyed.
In light of all that, suicide shooters have to be much more dedicated and intelligent. To join the Afghan army or police you need two letters of recommendation from your village or tribe. These can be forged, but increasingly these references are carefully checked. Another precaution is running an applicant's digitalized fingerprints through the databases maintained by the Afghan government and American intelligence. This makes it difficult for anyone who has been picked up, or arrested in the past, to join. If the terrorists gets past that, they have to keep up the façade of a loyal (to the Afghan government) recruit. This will be more difficult as more instructors and fellow recruits scrutinize the new guys for signs that they are on a suicide mission.
Victims of suicide shooters account for less than one percent of foreign troops killed in Afghanistan. But the Taliban also take into account the distrust it might cause between the foreign troops and Afghan security forces. This is not as big an issue as you might think, as the suicide shooters are hated by Afghan troops and police as well. The Taliban are, however, encouraged by the big play such attacks get in the Western media, which tends to ignore important details and concentrate on the drama.