Opera Mini is required to MITM by its design; it can't render HTML, only OPML fed to it by Opera's servers. I don't know what exactly the security implications are.
Sorry about that -- I was wrongly convinced the Opera technology was called OPML, too. I was a little bit surprised by lack of Opera-centric results when googling it...
Yeah, the best I can come up with is that you have to trust them that the data never makes it to the disk. But then they don't seem to be disk caching anything at all.
