Recently, Google Adwords made an announcement, on their blog, that Adwords stopped serving Ads sometime around 1:40pm pacific time, on June 29th, 2010 and lasted for about 3 hours. Nothing has been announced as to what caused the glitch at this time. I had a few inquiries go out to some of my Google reps, but it seems even they have been kept in the dark at the moment and very few people know the full situation in detail. While not greatly affected we could certainly tell looking through our reporting that something was up with Adwords.
I did however do some quick math based upon Google's 2009 financial tables. Last year, Google made over $22,889,000,000 in advertising revenues, which includes Google and Google's network sites. These two areas were affected by the downtime. With some math, based on 365 days, you can figure out that 3 hours of downtime would have contributed to approximately $7,838,698 plus change, in loss of revenue, and that's not even calculating this year's growth into the equation.
Google updated their blog around 4:40pm to let us know that the situation was completely resolved and that they are working to prevent something like this from happening again.