Unexplainable large number of cycles of MacBook Battery My battery is a year old, but it has 189 cycles. Why is this? I always use my MacBook with the charger plugged in and very rarely without the charger.
I disagree with the previous answer. The Apple battery is designed to be discharged infrequently, for instance around once a week - this is how to get optimal life out of it (see here) - you can safely operate it on charge for about a week before needing a discharge. Provided you exercise the battery occasionally, it'll be fine.

Also, the battery does not cycle when it is on charge - Matt Love is incorrect. A cycle is defined as the battery dropping below 50% and returning above it - which doesn't happen when running from a charger. Approximately one cycle a week will give you optimal longevity before replacement. My battery is a little over two years old, and on 1-3 cycles a week I still get 80-85% of the original battery life out of it. 

Letting it die down as often as possible will not improve longevity - this is a common misconception but in the case of Lithium Ion batteries, more cycles = less life.