It used client software installed on the user's computer, as well as data caching on Google's servers, to speed up page load times by means of data compression, prefetching of content, and sharing cached data between users.
[1] It was discovered that Google Web Accelerator had a tendency to prevent YouTube videos from playing, instead displaying an error message stating that the video was no longer available.
Google received and temporarily cached cookie data that the user's computer sent with webpage requests in order to improve performance.
[2] In order to speed up delivery of content, Google Web Accelerator sometimes retrieved webpage content that the user did not request and stored it in the Google Web Accelerator cache.
[2] Some privacy experts expressed concern that Google could "combine personal and clickstream data with existing search history data contained in Google's own cookie to create a far-reaching profile" on users.