The following can be found under:

6. USE OF SERVICES

Opera Turbo: When Opera Turbo is enabled, it will request normal Web content through an Opera Software proxy server. Opera Turbo will exclude Web pages located on an intranet or by using secure connections (HTTPS). The browsing experience may change due to increased Web page loading speeds when using Opera Turbo. We reserve the right to change, impose prices for, limit usage of and/or discontinue the Opera Turbo service at any point in time.

Opera Unite: Opera Unite is service whereby Opera provides users with a Web browser communication platform through a bundled Web server to share content, collaborate, and interact with others. Certain features of Opera Unite allow you to post and send content and/or links to User Generated Content stored on your computer, which can that can be viewed and/or accessed by others.

Opera Software ASA
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NORWAY

From what I've read elsewhere, Opera Turbo is mainly for dialup connections. Does it help with the speed of broadband connections at all? I'm not sure I would want to browse through their proxy servers, though.

Where do you find Opera Unite? Was this included with Opera 10? I've looked at the Opera Help and it says that it's in "Panels" but I don't see it there.
Isn't this a just way to set up a p2p network within your browser? With the right security, I can see this being very advantageous for businesses in exchanging MS Office documents.

You won't see any noticeable speed difference on a broadband connection.

All data being routed through a proxy server can be a security concern, but I don't think you need to worry too much about it. I use Opera Mini on my cell phone every day, and all sites run through Opera servers which compresses the pages to a smaller size so they load faster on mobile connections (they look the same as on your computer, they just use less data).

Its not included in Opera as yet, it's due to be in the next version - 10.10

That version was released today. SEE HERE

Only as beta though (before anyone goes rushing off to download thinking otherwise )

Yes true, it's Beta. I felt confident posting that version though, because I've never had a single bug or crash when any of the Opera 10 preview/alpha/beta/RC releases.

Still, those wary of Beta releases should be aware that the final version of Opera 10 with Unite isn't out yet.

Almost all of the Opera alpha/beta/RC releases I've tested have been stable for me, like TeeJay, so I would be pretty confident about testing out one of Opera's betas.