There is a thread at WebmasterWorld where AdWords advertisers are discussing the impact, if any, the Olympics is having on their ads and site performance. One member reports "10% less traffic" whereas an other agrees;
Traffic and clicks were down about 10% however the EPC and eCPM remained good therefore Saturday ended up a good day.
For some reason, most of the responses indicate a lower amount of traffic, but higher performance on the site (such as conversions and pageviews).
Forum discussion at WebmasterWorld.