I haven't read the whole thread, and with it going into 3 pages now, this may have been stated, but...
I think there are a few reasons most of us see our accuracy drop off when shooting small pocket/pocketable pistols even though the inherent accuracy is there.
Of course the shorter sight radius makes it harder for most of us to be as accurate. That seems to be pretty intuitive. Most also have smaller sights which can make it harder for most of us to shoot it as accurately as with a larger gun (some, like my LCP have barely any sights). The smaller grip can make it harder to grip properly so the initial shot may be off, and regardless of how well you shoot that first shot, can make sight recovery and follow-up shots a bit off. The light weight of these guns, especially when in a relatively powerful .380 or 9mm chambering (as opposed to the more traditional pocket pistols with light recoiling .32ACP, .25ACP or .22lr), can make quick follow up shots difficult and contribute to poor shot to shot accuracy. Also, the light weight and perceived recoil can lead to flinching and anticipating the shot which can lower your accuracy.
All that said, I do find my SIG P290RS to be quite accurate (and low recoiling) for its size. It is about as accurate as a traditional subcompact sized gun (SIG P239, Glock 26/27, Taurus PT 111/140 Millennium Pro). I have also found that the metal micro Kahr (the Kahr MK9) is pretty accurate for the size, but the light PM9, while better than many of the lightweights, is still tougher to shoot accurately. There may well be others that are designed in such a way as to minimize the accuracy issues of the typical pocket sized gun.