As Jerry says, it is all in how you count the moves. The number 108 was used in the old days just because it was easy to remember. The number itself is pretty arbitrary. The Ch'an Buddhist rosary, the nien chu, had 108 beads, and people would go over the forms in their head or say the form names out loud while they counted the beads with their fingers.
This is purely hearsay, I don't have any evidence to confirm it, but I've heard the story that the PRC govt. has discouraged the use of the number 108 in Wushu training because of its former religious connotations...
The Tung family and the Wu family, who moved to Hong Kong in '48, still use 108 for their forms. The Wu family members who stayed in Shanghai use the number 89 for the same sequence.