[a1a]

1) Is that really a bad thing? Isn't it generally a good thing that law enforcement finds law-breakers?

2) So do drunk drivers that crash.

3) You're arguing against yourself. Yes, it's bad that bad guys get notified so they can avoid checkpoints.

4) Shouldn't law enforcement spend their time enforcing the law? It's well spent time IMO. As you say in (1), they also solve other more serious crimes (e.g. finding wanted criminals)