Design Engineers are told not to concern themselves with patent infringement when developing a new product. Cost and performance are the key success factors. If the new design infringes, let the patent holder find out and tells us. Our lawyers will handle infringement issues.

I was told this while working at a fortune 100 company, and I beleive it's common practice, and it actually makes good business sense. Having engineers search through patent files to see if they might be infringing would be crazy. If they are ever discovered infringing, the infringing company can always say oops, and then spend years discussing/negotiating/delaying a settlement.

That's how it works.