For those asking, the various default themes are indeed the most popular themes. However, to answer a couple points:

1. The "downloads" that come from updating core and thus getting those themes installed at that point in time do *not* count towards the popular list. Only downloads of the theme ZIP file from WordPress.org count.

2. There's no special treatment for the popular list. The various default themes do not have an automatic entry in that list. It's based on the download numbers alone.

Now, I suspect that simply having that large pre-installed base does indeed cause those themes to be downloaded more often, especially when updates occur. So, they're at the top of that list because of that, but there's no guarantees there.

Also, as I told Jeff, I do not believe that the inflated download numbers for the Swift theme was their fault, nor does it appear to be intentional. No blame falls on the authors for the changes made, even though they were probably most impacted by it.

Note to anybody making an automated installer system: If you're going to pre-download a bunch of themes from WordPress.org for users, so they have a selection available to them immediately, please do us a favor and append ?nostats=1 to the end of the ZIP file download URL. Makes things nicer for everybody involved. Same goes for plugins or any other sort of downloads where the download is not actually directly user-initiated.