I asked this on a recent project management course. The project manager looked very sheepish. Yes, there was a risk log; yes there were activities to reduce the risks and yes they allocated responsibility to individuals to mitigate the risks.
Have a review date and stick to it. The project manager should take responsibility to ensure risks are mitigated. Individual should also take responsibility for risks they are managing.
Oh and by the way; there were a good few on the course like this project manager!