I like the idea of keeping track of seemingly useless things, because the statistics gleaned from such data always seem interesting.
As an example, one of my friends recently called me and informed me that he was missing some money. You see, he's been keeping track of his finances using double-entry bookkeeping (which means that he sees not just where the money went to, but where it came from). He had been tracking cash that had been going into, and coming from, his wallet, but had not kept careful record of every little transaction (all the little things that we don't think about, like parking meters and vending machines). Looking back over the past several months he discovered that there was a severe discrepancy.
"I'm missing almost $700!"
If we rule out theft and loss -- both of which seem improbable given the data -- that's a lot of money to spend in small amounts. But that is, of course, entirely possible, and it makes you think. In my case, I wonder what the statistics are for my various categories of purchases. For instance, how much money have I sunk into Chipotle's guacamole (which costs me about 12 minutes of work at my current salary)?
When you have statistics, you can make reasoned economic decisions. As an example, I recently checked my statistics in X-Moto. Since March, I've played for 66 hours. Much of that time has been spent trying to beat several of the most difficult maps. In particular, I've played the map "Up and Down" 1624 times in a total of 11 hours (and I still haven't beaten the stupid thing!).
Thanks to these statistics, I've made an economic decision not to spend my time playing X-Moto anymore. Where will my next five- and ten-minute time- waster come from? I haven't the foggiest, but I doubt it will have such wonderful statistics attached. ...Although I know I spent 44 hours on the phone last month...