Crashes occurr for various reasons. Explosions seem to be the biggest cause. This is why you dont see many servers with grenades, because if you had a bunch of people throwing grenades around it would crash the server every 5 seconds.
There was a beta test recently where they asked us to spam with rocket launchers to test the stability of the next update which is supposed to come soon.(And apparently this update isn't 0.4, but just a smaller update to fix some bugs and crash issues.)