Today's xkcd comic depends on a very common, but unjustified economic equation: that time is money. More precisely, I am objecting to the practice of using a person's hourly salary to evaluate the amount of money lost when that person wastes one hour of his time.
Granted, if that person wastes time during working hours, then he costs at least that much to his employer. At least as much, because employers expect employee work to yield returns over and above the cost of their salary; otherwise, it would be economically pointless to have employees.
But why would the employee himself be deemed to lose that money? If he wastes his time during office hours, he gets his hourly salary anyway. If the time wasted is not during office hours, then the opportunity cost of wasting this time is zero: had he done something else with his time, he would not be earning any money either.
Perhaps "time is money" only applies to startup founders, whose startup-related work directly impact their bottom line. But this line of thinking works precisely because founders don't have an hourly salary; rather, their net worth is a function of the worth of the company they own. So it still doesn't make sense to compare time and hourly salary.
That being said, I still think that Time is a very precious resource. I want to enjoy every minute of it; I just don't buy the idea that I'm wasting money doing so.