Nokia don't care about Trolltech's cross-platform technology - they're just after a quick and cheap way to get their own Linux platform. Why? Because Apple has one and Google has one - so Nokia has to have one - simple as that.
Not that they aren't in need of a next-generation platform. Symbian really is ready for the knackers yard, and I guess it can't have been much fun being shown up so badly by an upstart like Apple, but I can't really see Trolltech bringing anything very valuable to the table.
Their technology might be very clever, if you want to write something that runs cross-platform, but like I say - that's not Nokia's problem. They want a platform to compete with iPhone and Android, and that means they need something which is highly optimised to get the very best out the hardware they have. Compare the fluidity of the UI on the iPhone to clunky, slow S6O UI on the N95, and remember they share very similar hardware, and you'll see that they need something a bit special to catch up.
Also - I can't help feeling that Android's approach of exposing all the low-level functionality of the OS as Java callable libraries, so that the high-level apps can be written in Java, is likely to produce a far more productive development environment than insisting everything's written in C++. It would also allow for some sort security environment to be implemented if that was required.
So - Nokia and Trolltech. The wrong aquisition of the wrong technology, by a company that has lost the will or the balls to develop any decent technology of it's own.
Let the flame war commense!