Interesting thought Phill
Release 184.108.40.206 has 6,164 downloads in 8 days to date.
Most people do not list their pages on the mojoPortal page: Sites Running on mojoPortal. For example, me and my manager have 10 sites and none are listed there. Also... I download mojoPortal code once for 10 site upgrades so that skews the usage of download statistics/site.
Also, some sites also remove the text "Powered by mojoPortal" footer which would skew Google statistics.
I think WordPress and DotNetNuke and others would all have the same issues. It's just a difficult and maybe unfair to guess.
As a developer I might hide a piece of code in a C# dll that would do an HTTP Post to the main mojoPortal Website once a month and then the main site database could collect accurate deployment statistics. But maybe a "Call Home" script like this would not be considered proper to hide in the code.
I'm just a mojo user like you Phill and this is just my 2 cents.