Originally Posted by FBinNY

Based on some incidents in the last few years, there's increased concern over the possibility of terrorists coming in through our very porous border with Canada. Moving check points around randomly inside of the borders is just another line of defense.

They've been using similar methods all over the world for decades, and it seems to be something of a deterrent. And I can assure you that in many places these checks are taken very seriously. Having soldiers take line of fire positions surrounding you car while someone asks where you're coming from and going, then explains that "this isn't on the way to Paris" and asks to see your papers reminds you that security is something we've always taken for granted here in the USA.