As a way to preserve the Wing Chun system and to prevent modification, the sets have been constructed so that the number of movements in each set is 108. The 108 number is in honor of the 108 martial artists who died for some good cause. We don't have any more details on these people at the moment. The number 108 seems to have been borrowed from the Indian Hindu religion, where the number is very popular. There is supposed to be a temple in India with 108 sides.
The classical Wing Chun system has been elegantly structured into five logical pieces. The three hand sets, the wooden man set and the weapons section. Today, most versions of the third set have a count of more than 108 movements, but if the duplicate elbow sections are removed, (which don't add any new information to the set), then the count is 108. We will discuss this in the future. The knife set has 82 movements and the 6 1/2 point pole form has 26 movements.
Summary
108 = 2x2x3x3x3 (5 factors)
Live Dummy
The live dummy was the first dummy set Grandmaster Yip Man taught. Master Wong Kiu learned this set before the first wooden dummy was ever built (by the Cheung brothers). After the wooden dummy was built, the live version was not taught.
Note: July 1995
Note most people don't care about the 108 count topic. Having a math background, I found it an interesting point for speculation. Future viewpoints will present other discoveries related to this topic.
About the point of not everyone learning everything: this may have no significance whatsoever. I doubt if it was because things were a big secret. The Wing Chun system is not a secretive style. In our own club we practiced Wing Chun weapons fighting in the early 1980's, then we went for ten years just not getting around to it because students were not ready for it yet or we were too busy with other things. I don't imagine there was much room in Hong Kong for pole fighting so that may be all it was. Also in general, classical weapons fighting is viewed as impractical by most people because of the gun. But some of us like to preserve the art.