There have been a handful of widespread outages since Google Analytics was first rolled out. They have typically been rare and brief, but they have been troubling for users nonetheless.
Outages have affected users in two ways:
1. the Google Analytics interface has been slow or inaccessible
2. traffic data has been lost
Some users report that page load times on their own sites became slower, too. Fortunately, outages do not affect the websites of users who have set up the code correctly.
Since the Google Analytics interface is hosted on Google’s servers, an outage can affect your ability to log into your accounts. Or, it may affect the load time of the report pages.
If there is a widespread outage, __utm.gif requests won’t be served or logged, and data for that time period will be irretrievably lost. Historically, this has been the exception. Typically, data is delayed but not lost.