[lucumo]

> Of course, they don't tell you this anywhere.

I wonder where you got the knowledge from then...

Perhaps you learned it from the help that comes with Opera:

> "The technology behind Opera Turbo is a proxy server with server-side compression of Web pages. A compression rate of up to 80% can be achieved, in part by reducing the quality of images. If you want to view an image uncompressed, right-click on the image, and select "Reload Image in Full Quality"."

[extension]

I learned about it from a blog, which is a lot easier to find than that help page. Since the feature requires zero skill to use, the only people I see going to Help -> Opera Help -> Opera Turbo are those doing detective work, or possibly some non-tech-savvy users, who will not know what a proxy server is or understand the privacy ramifications.

When Google added PageRank to their toolbar, they forced you to read at least two warnings before you could use it that said, in big letters, something like "PLEASE READ THIS WARNING.. IT'S NOT THE USUAL YADA YADA".

At the very least, that's what I would expect from anybody, but especially from a browser, a piece of software that users put an enormous amount of trust in. I've managed to find a few mentions in Opera's marketing material that this feature goes through their servers, but no hint that there is any privacy issue.