[imglorp]

For an authoritarian police state, false positives are fine as a show of force.

If the system mistakes you for someone else, you might get your door kicked down, your dog shot, and get dragged in and interrogated. Then you will come to realize what will happen if you really run afoul of them. So maybe you think twice if you're planning an infraction in the future.

So they may well want to round up the top N suspects, knowing that N-1 are innocent.

[Balgair]

Yes, but this is a separate issue than surveillance. You can have totalitarianism and surveillance just as well as with democracy (not ever typical though).