This feature has been shown to reduce the size of web pages by 50%.
That means data about your session with Techworm will be stored/saved/noted somewhere.
But then you dont use Opera for your private communications or posting/seeing/sharing confidential and eyes only information.
The use of the compression proxy does not require you to have a Google account.
If you are a privacy oriented user, it is suggested that you disable this feature.
source: www.techworm.net