As I noted below (likely going to be voted down for being uncool even if accurate), just painting crosswalks may significantly increase pedestrian risk by attracting crossings to dangerous intersections. So don't get too energized.
Most real efforts here include OTHER steps to calm traffic, and then a painted cross-walk is added to attract pedestrians to that area. I hope Boston is doing more than just slapping crosswalks down with paint on high speed multi-lane roads - because people will be killed. Reducing lanes of traffic where peds cross, slowing traffic (stop signs, lights, speed limits with enforcement) all are much better starting point.