All Things D writes, The often-cited expression “When something online is free, you’re not the customer, you’re the product” is compelling and smart and seems to sum up the problem of living in an advertising-supported online world. But it also stops too short. People trot out this line to advocate disengaging from a world of personalization and privacy scandals. The thing is, you can’t. In this day and age, avoiding security cameras and credit-card tracking and traffic pattern analysis and mobile location data would require a massive bulletproof signal-blocking hermit-crab shell. What you can do is…