From Jason Kennedy Ubuntu: Wake up and smell the Unity against you:
In the past few months, Ubuntu seems to have experienced a serious drop in popularity. It can be said that Linux distributions rise and fall when something new becomes the latest and greatest, but this turnaround seems sudden and could possibly be due to some recent design changes on Canonical’s part.
Canonical switched Ubuntu over to the Unity user interface, and a correlation seems to have occurred between this and a slump in its usage numbers. Royal Pingdom has recently compiled data from DistroWatch which seems to confirm what many have been saying about Ubuntu’s popularity: The number of hits to DistroWatch’s Ubuntu page is down 47% over the last 30 days, where Mint is up 105%. Note that the statistics are based on the normal amount of traffic for 2010, and that DistroWatch itself has doubled in size this year. What it means is that overall there’s been a decline in users searching for Ubuntu Linux, and also a huge rise in those users searching for Linux Mint.