What Are The Hot Research Areas in Concurrency Theory?

Yesterday Andrei Sabelfeld (Chalmers University of Technology, Sweden) visited ICE-TCS with Arnar Birgisson, a former master student of mine who is now doing doctoral studies under his supervision. Andrei delivered the seminar Information flow in web applications in the ICE-TCS seminar series (the abstract for the talk is here), we talked about liveness and safety properties and about academic matters in general. We at ICE-TCS enjoyed his visit a lot.

Over dinner,  Andrei asked me:

• What are the big unsolved problems in concurrency theory?
• And what are the hot research areas in the field?

I gave my quarter-baked personal answers, but I'd like to hear yours.

I have the feeling that research in concurrency theory is driven more by "hot research areas" than by collections of big open problems, but that's just my personal impression, even though at some point I started collecting a list of open problems and stated some in this essay. 

Also, how much does the "hotness of a research area" inform the research you do and that you suggest to your students? For what it is worth, for good or for worse, I mostly tend to follow my own personal interests and inclinations rather than the directions of the field at large. However, one  has to "sell" one's work and have it published. It is undoubtedly easier to do so if the work is considered to be hot and timely by a substantial fraction of the research community. Doing work in areas that are considered "important" by many will probably also give a student better opportunities to find further employment.

Overall, I feel that it is important to give one's students a good problem to work on for her/his dissertation. There are certain characteristics that a good problem should have for sure, but is "hotness" one of those?

Addendum: There is a lot of good career advice for everyone here.