A WebmasterWorld thread reported that Google AdWords analytics was down on Friday, along with Google Finance and other Google services.

AdWordsAdvisor confirmed this at around 2pm (EST) on Friday, stating:

Hi all - thanks for the heads up. Engineering is aware of this one, and is working to resolve it asap. No data has been lost - it's just been delayed on its way to your account. ;)

Thanks for your patience, and my apology for the inconvenience.

So no data should have been lost.

Reports of the analytics coming back up began coming in Saturday morning.

Forum discussion at WebmasterWorld.