I have had this problem with my cuddeback (older 3.0mp model). Maybe I only notice it when it snows, but I will get a lot of tracks in front of the camera that the camera misses or wont trigger, see pic for example. This was the first picture taken after it snowed that night, look at all the tracks in front of the camera that were there before the pic was taken, how did the camera not trigger??

http://im1.shutterfly.com/procserv/47b7cc25b3127cceb16aa87c51ea00000026108UbuWTdu3I