Why is there a cop on every other corner?

Just wondering if anyone knows whats going on? On almost every other corner or so, there is a police car with lights (no sirens) and an officer standing next to it. Its like they are waiting for a parade or some event that will bring lots of people to the neighborhood.

That's part of the oft sited terror task force stuff. In this neighborhood, rather than the mass congregation like they do at GAP, Times Sq, etc. they show up and park at the corners of each block on a major thoroughfare.

They were out in force yesterday afternoon, evening and then again this morning.. seems kind of strange..