For about 4 weeks, starting September 28, page view stats for Wikimedia wikis were highly inflated. Close inspection revealed this was an artifact caused by a software change.
New code for page banner handling generated extra requests to the server in a format which
made these requests be seen as extra page views. This has been fixed.
Fortunately these inflated page view counts could be patched by substracting page views for the identified non-pages.
See also up to date Wikipedia page views table.
Trend over 3 years
The line plot below (used to analyze above anomaly) shows page views on major Wikipedias since we started collecting data.
1) The red line shows the peak in page views for the German Wikipedia caused by the public outcry over a court order which temporarily blocked access to the German Wikipedia or at least tried to do so (in fact only the ‘wikipedia.de’ alias was blocked).
2) The plot also shows when the previous anomaly occurred and for how long, and more or less how much data got lost. In the full sized plot (click image) you can clearly see how the weekly pattern (lower traffic in weekends) got disrupted from late November 2009 till mid July 2010. In this case only results from April till July could be patched from still available logs.
Incidentally you can also see from the page view stats page how Chinese page views have dropped considerably from May 2010.
[update] Members of the Chinese Wikipedia community explained to me that the probable cause for this is a modification in access guidelines for search engines (robots.txt), dating from May, which meant to better distinguish zh-tw and zh-cn link versions. Several weeks ago these guidelines were re-examined and updated. This should have a positive effect on traffic volume in the near future.