Google Web Accelerator sends requests for web pages, except for secure web pages (HTTPS), to Google, which logs these requests. Some web pages may embed personal information in these page requests.
Google receives and temporarily caches cookie data that your computer sends with webpage requests in order to improve performance.
In order to speed up delivery of content, Google Web Accelerator may retrieve webpage content that you did not request, and store it in your Google Web Accelerator cache.
It has been discovered that Google Web Accelerator has a tendency to prevent YouTube videos from playing, with the message in the YouTube video player, "We're sorry, this video is no longer available." By simply turning off Google Web Accelerator, the user should be able to play YouTube videos again without a problem.[2]
It was also discovered by Subnet1 that most videos can be fixed by entering .cache.googlevideo.com into the "Don't Accelerate These Sites" section in the preferences.[3]
As of September 2008, the Google Web Accelerator is not compatible with Firefox 3.0.