I have seen it coming. Nokia have been living in their comfortable telco-friendly niche for too long.
1. They have a ton of low-end models, each one seems to have different menus and a lot of missing features, as if telcos got to choose what features to remove so that they can try to sell a new phone contract every year.
2. Their middle-range models also lack in features and the quality does not always reflect the price. I paid 240 EUR and the side keys fell apart in one year.
3. Their high-end phones were basically show off pieces without a proper or at least not developed enough eco-system.
4. Their PC software has become a bit too bloated and it has some basic bugs (some MP3s not showing on the phone list, disk crawler locking up files...).
The combination of these drive many low-end users to experiment with other companies phones and most high-end users to try iPhone or Android.