I agree that roundabouts are horrid. Agreed that picking fights with motorists is more or less wasted effort. I do keep a running mental note of dangerous intersections.
The intersection of the BU bridge and Commonwealth is notorious. On one occasion I had no choice but to cross Comm Ave at that intersection and felt highly exposed and understood why it is so dangerous. A friend of mine recently got knocked over by a too-close right hand turn on Beacon approaching Cleveland Circle.