The article only compares Windows hosting numbers. It does not include Linux. I think for Amazon the number of Windows hosts is relatively small compared to the total hostings...
The article clearly says "In the February 2014 Web Server survey Netcraft found 27,000 web-facing computers (both Windows and Linux) using the cloud computing platform."
Yes, that's the total number of web-facing computers found on Azure, of which 23,400 are Windows-based. Amazon has 22,600 Windows-based web-facing computers, which puts it in second-place for world's largest Windows hosting company.
They never directly compared the Linux-based web-facing computers.
It appears that this is mostly due to the growth in Azure, and that that growth is primarily due to Microsoft cloud-hosted services using Azure. (The article does state that part of the growth is due to internal MS stuff, but does not give any indication about the relative amount of MS machines vs third party users' machines.)
True, but what else would you think it would be compared to.
It appears to use number of domains as the measurement, not sure if sub-domains are included in that, but either way, is there reason to believe that Microsoft is running considerably more domains than Amazon? Sure they have more products, but not thousands more.
Therefore, I think it is safe to assume that most of these 'web facing computers' are customer servers, and if so, that is a telling sign for Azure. AWS has been in the marketplace longer, and has the mindshare. I'm surprised to see Microsoft anywhere near AWS numbers.
A typical vendor-sponsered research result :-)