Apart from that, we already know the Chinese have hacked GMail accounts on several occasions, so Google is already a definite target and the Incidents that have been reported may be just the tip of the iceberg so far as we know.
We also know that there have been cases of corporate and government espionage in the recent past. This is happening, right now, and we may never know how extensive it is. It's entirely possible that Nokia could become a target of either technical or even employee infiltration. If so, covert access to a service like this would be a fantastic coup, especially since Nokia phones are still popular in many parts of the world with unscrupulous and technicaly sophisticated governments.
Recent mishandling of user accounts by Sony Entertainment and LinkedIn gave us a glimpse of how much damage an intrusion can cause, even though (?) their management thought their intended purpose couldn't lead to any serious liability (speaking through my hat here).
These servers probably do, as I'm sure some people use them to do online banking and shopping online.
When I access a proxy on my computer, it can't do that. If an arbitrary proxy could MITM a secure connection, HTTPS would be useless.
So I presume the Nokia browser is complicit in this scheme.
google chrome sends all my pages to translation and what-not. I have to completely trust it. that's why i never use the compiled version but the chromium one only (hence not having access to any addon via the addon site, have to do some manual work there)
Even besides the browser, how many computers don't I see the skype button next to phone numbers? would you trust skype is behaving and not sending your data to their servers? did you remember to disable this add-on for ssl pages?
A browser based on an open-source codebase with many people auditing its source-code and network traffic (there was much paranoia about Chrome when it was released). And even in that case, you have the choice to use a completely open-source browser that has a different stance on user privacy (Firefox).
An NPAPI plugin that can be easily disabled.
A third-party BOX MITM all your secure connections without your knowledge.
I don't think the above are comparable in magnitude.
Do you trust your phone operating system? How do you know it is not capturing your data when you access a bank website? Same issue here.
The one difference is that the Nokia servers might be a bigger target for hacking, instead of hacking individual phones.
On iOS this comes up after connecting to wifi as a reassuring, secure-seeming, official-looking page that pops up inviting you to accept the new certificate. Do so and boom, you're vulnerable to a MITM.