Back in the 1990s, when I started my first company, I recruited Jim Fitzsimmons to take over as CEO so I could finish my MBA.
(Side note: Jim was an All-American basketball player in college, when he starred for Harvard along side future broadcasting legend Jim Brown. Jim and I would occasionally play ball together at the YMCA by our office; his knees were shot and he was in his 50s, but he still had a sweet stroke on his shot)
I learned a ton from Jim, who shared a lot of hard-won wisdom with me. One of the sayings I remember most was, "You get what you inspect, not what you expect."
Jim's point was that unless you measure performance and manage accordingly, your startup's performance is likely to disappoint.
I've tried to follow his advice ever since, but I've also learned to value the corollary, which is to be careful what you measure.
Take Klout, the most prominent measure of social media influence. It takes a highly complex thing--the nature of influence--and reduces it to a single number. This leads to what I call the US News & World Report effect--students think whatever school is higher in the rankings must be better, rather than doing the hard work of assessing actual fit.
I know this, yet I'm still aggravated when I compare my Klout score to various friends, or when it mysteriously falls. And I'm pleased when it rises, even though I have no idea why, or what it means.
Be careful what you measure, because you'll almost always end up judging performance based on that measure--whether or not it's a valid one.