Okay, I guess I'll chime in on this one.
I used to be pretty dilligent about changing out cracked windshields, having heard the whole "structural integrity" thing repeatedly. That was before I moved out to Montana. Out here, you would be really hard-pressed to find a vehicle newer than about 5-years old without a cracked windshield. I replaced one windshield since I moved out here and the darn thing was cracked within the month! Between the sand & gravel on the roads and the extreme temperatures, they never last long, and it's only a very nice car you bother to keep putting them in.
So what makes me skeptical is the fact that you never, ever hear about a damaged windshield as a contributing factor in a fatal crash. Also I've handled windshields both intact and cracked and, while one that has been actually punctured or has damage bad enough to change the curvature is obviously weaker, I have a really difficult time believing that a simple crack or even a network of superficial cracks caused by rock chips reduces the structural integrity of the windshield in any meaningful way. And its those cracks that people are driving around with-- you get a hole or a baseball impact, of course you go get it changed. Ditto for causing blowouts-- I'd bet deteriorated seals are to blame for this, which would get changed with the cracked windshield, but that doesn't make it the crack's fault.
Okay, so granted I haven't really examined the body of scientific work on the subject (if there is such a thing), but out here the common belief seems to be that any claim that a broken windshield does anything other than look bad and maybe impare your vision is at best an exaggeration and at worst a total fabrication by autoglass companies. I'm not entirely sold that its all bunk, but I am quite skeptical.
Oh, and for what its worth, I've never heard of anyone getting a ticket for a cracked windshield and we have no inspections of any kind, so I can't really comment on the legal ramifications.