Re: um, correct me if wrong but.....
Ok, I'll bite:
No, it is not just a 'home web server' that you can get elsewhere.
The "web server" part that Opera mentions is that the browser supports two way HTTP transactions, so it can respond to requests as well as making them. In essence it is a Peer-to-Peer networking client/server application using HTTP as the transport protocol through port 80. Responding to HTTP requests makes it technically a "server". That's it--no magic, no Apache, no IIS.
Moreover, it is not just another 'cloud' application. "Cloud computing" harks back to the elden days of yore when dumb terminals communicated with centralized mainframes which performed all the processing and storage for them. Or to the past "Online Services" which served as gatekeepers of information, and jealously controlled its access. The Internet and the World Wide Web--along with personal computers--were supposed to break us from those shackles and allow individuals to directly form part of the whole framework, sharing and connecting to each other directly. The Unite platform is a return to this original intent: Yes, it is a "cloud" but it is not in the shape of Google or Amazon or Microsoft, it is amorphous and comprised of each individual computer on the Web (the reason why it was originally called so, and not something like "World Wide ISP Network".
However, it is more than this. It is a platform that exposes an API for extending the transport and sharing services. They call these "Unite Services", and are nothing but simple web applications built for the Unite platform. Once these are installed and turned on on a user's machine, these applications offer interactive services to the local and external users, and they do not need anything more than a regular web browser (any browser!) to access.
Part of the genius of the whole thing is its simplicity: there is practically nothing to it, so for the average person this is a dream! If my mom wants to share her pictures with our family, why should she have to upload them to a third party server and be bound to their terms, which may even include property claims on the media assets themselves, when she has a perfectly good and reasonably fast computer and internet connection? All she needs is an easy-to-use interface that will allow her to share them from her own computer and send a link directly to us. This interface is what Unite provides.
The security of the system so far seems to be an all-or-nothing affar at the moment: You either share publicly everything within the shared directory without a password, with a password, or you don't share at all. However, it is only in Beta stage, and the Opera developers have commented in the support forum that they are working on a more granular permission system. As before, Opera seem to have taken security as a major concern when designing this system.
In any case, I hope you try the new Opera Unite browser for yourself and see what it's all about before making assumptions based on hearsay and prejudices. It is truly an innovative platform in that it fullfills promises heretofore forgotten by most, made at the inception of the World Wide Web itself.