Kexi is an open source visual database creator, and is distributed by default on Kubuntu. Kexi features an opt-in usage statistics collection program. The stats collected are information such as the KDE version, Linux distro, machine type, screen resolution, etc. K/Ubuntu has topped the chart, being the most used Linux distro used to launch Kexi – sitting at 47%. It’s not possible for Kexi to distinguish between Ubuntu users running KDE or Unity.
For other stats, take a look at the full post on blogs.kde.org. It should be noted that these information are from people who have chose to opt in to usage statistics collection, so the actual stats may be different.