It's a fair question, hypothetical question asker, and there is data to back up the claim, though a complete 'splainin' may not be forthcoming.
As I have written before, I am nearly as fascinated by the statistics of my blog as I am in the blog itself. The general trend in readership here at Lotsa 'Splainin' 2 Do has been on the upswing over time, but in the second half of December, there have been a lot less readers than there were in the first half of the month. I wondered if the shift was a sign of disenchantment with my prose stylings or part of a web-wide trend, one which will hopefully reverse in the near future.
I visited some of my blog buddies who use the Site Meter software to keep track of their stats and make the information available to the public. I took the day by day info of visits (the bar height in yellow) and page views (the extra bar height in red) for November 25 through December 25 for my own blog and five others. I scrubbed away names and the scale for the bar charts, because I was interested in each blog's popularity over time of the past month, not their relative popularity to each other.
While the blogs in question cover a lot of different topics and styles of blogging, publishing this data in a real statistical context would not be considered kosher, because this would be a convenience sampling.
Looking at the data, there are some common trends, though some of the six fail to show some of the signs.
The Christmas Day abandonment: For every blog except Blog #3, Christmas Day is the lowest readership day of the sample, and in Blog #3, it's the second lowest day. It's almost as though people are stepping away from their computers on December 25 to spend time with their family and friends. This is just speculation on my part based on a small sample. I'm sure a government funded survey using a much larger sample could be undertaken to check this crackpot hypothesis.
The mid-month spike: I have no single 'splainin' for the mid-month spike, but you will notice in blogs #1 through #4 all have a day or two around December 15 when readership increased significantly then fell back to normal. The two big news stories of the time period were the shoe thrower in Iraq and Blagojevich being arrested, but not all of these blogs covered these stories. Blog #5 has the steadiest readership, with no one day showing massively more readers than any other. Blog #6 has a cyclical pattern, but it doesn't perfectly follow a seven day trend.
The late month slump: Like the Christmas Day abandonment, every blog on the list has a period just before Christmas were readership is down compared to late November and early December. The least affected blog in the late month is Blog #4. If we remove the big two day spike on December 15 and 16, it could be argued Blog #4 has an even steadier readership than Blog #5. Could it be that folks for some unspecified time period before December 25th are away from their computers more, preparing for some festivity that will take place on December 25th? Again, this is just a crackpot theory based on a small sample and one researcher's wild imagination. More study is certainly warranted before readers start throwing this factoid tidbit around at cocktail parties.