I'm willing to walk a long way - less long in direct ratio to how much camera stuff I'm lugging but I'll put the car 2-3 miles away if it's going to save me problems with security types and/or towing.
I always park in busy public places such as a bar or family restaurant, a business, a store, or group of shops. It's worth it - I never ever have to worry about not having a car when I get back, or tickets on the windshield. In lieu of a close-enough public place I will run a beater car right into a bunch of shrubs or tree cover when possible to do so, no one ever finds it.
When we were just up at Northampton hospital the layout was a real challenge. The way they've got it secured now, you cannot put your car anywhere on the grounds at all without being questioned. Because it was a Sunday I took a chance and left the car down on Smith College property. Smith requires a Smith sticker but their lots were all wide open, I found a little side road belonging to them and just tucked the car in off the side, no problem. Long hike in and out though.
I guess it all depends on how far you're willing to hike and your bug/snake threshold.