The WSJ has a piece today arguing that blog traffic declines massively when a blogger goes away on holidays, even if they bring in a guest host. Here is the chart it used to try to make its point:
Compelling, right? Look at those declines when Sullivan and Malkin went on holidays. Must be the holidays that did it.
Maybe not. In both cases traffic had begun to fall off before the two bloggers went on holidays. Why? Almost certainly not in anticipation of upcoming holidays, but more likely because we were entering the August prime summer holidays season. In other words, blog readers were on holidays at the same time as the blog writer, so traffic would have been down anyway. Seasonality strikes me as a more compelling explanation than the one offered by the WSJ.