I originally wrote this as a comment but I think it’s worth a post. I reported that Distrowatch saw a sharp increase in activity for the popular distros and was replying to a comment.
NetApplications is seeing something similar:
week of September 30, 2012, USA GNU/Linux =1.91%
month of September 2012, USA GNU/Linux= 1.59%
What big roll-out of GNU/Linux happened last month?
California, September, 8.81%
week of September 30, 10.46%
Yipee! It’s Mountain View, CA which went from 10% for September to 52% for the week of September 30. Did Google expand? Did a neighbour take up GNU/Linux?