Occasionally I'll go to the gym, load up a barbell then just leave. That confuses my muscles. I wonder why I still weigh 8 stone....
The idea of 'confusing' or 'shocking' muscles into growth is to prevent a plateau that's caused by growing accustomed to the stimulus provided to it. By doing the same workout ad infinitum you'll eventually reach your limits of adaptation.
By providing a new stimulus (more weight, less rest, different reps, change in tempo, different routine, new exercises, etc) you're creating an environment for new adaptation to occur. However, for best results this should be done in a planned, structured fashion rather than just sporadically adding in 100 curls or doing 20 chest exercises.
Used sparingly the ideas on the link above are a useful tool in your training armoury. Used too frequently and you'll dilute the purpose of doing them.