My understanding of the Hawthorne effect is that it is a temporary increase in performance due to the subject's awareness of being studied. I stopped using RunKeeper over a year ago but my default walking speed has remained much higher than it was when I started measuring it.

Except the Hawthorne effect is poorly studied, probably doesn't exist as its own effect, and is useful only as a metaphor for this very "What we measure we can fix" effect.