Okay, I think I see what you're getting at. Simply put, you'd like to know about the security-related issues a device such as the N9(50) brings along as a result of it being not only a computer, but a mobile communications device.

I think I've jotted down the most important of them in my post above - personally, I force 3G as a countermeasure against IMSI catchers since GSM is not up to snuff. The two aspects I consider the most important right now are that

• the N9 has a lot more means of receiving and sending data to/from the outside, so many more attack vectors
• many of the most crucial software components, such as baseband firmware, are closed-source and probably not too well audited, with questionable accountability

You hint at the latter with your question about Nokia Conversations. With closed source, we don't know too much at all until someone whips out IDA Pro . So, can't really say much about your specific questions. And firmware issues persist across operating systems, of course. Mitigation would in most cases be hard-as-nails to downright impossible.

With any untrusted network, you can gain some measure of privacy and security with virtual private networks or tunnels. You're not safe against traffic analysis, but it helps against eavesdropping and in-transit manipulation.