they then post a notice on the door addressed to the tenant that they are not allowed in the unit and if they attempt to go in without the landlord's permission, they will be arrested for trespassing. 

@Sean Cole  it so very different your seller is the Sherriff or trustee service in our case.. your buyer is someone who is bidding... and puts up a significant non refundable deposit.Or like in the case of Indiana its a felony to bid on a property and not follow through.. not only do you lose your bid deposit the Sherriff can have you arrested. 

Why do the cops not take names and arrest after multiple trespassing incidents?

You know that people can be arrested for abuse of animals or elder abuse or child abuse; if the stuff that I've seen in some houses were treated similarly, the owners would be arrested for housing abuse :)

@Alex NopeI wonder if you could schedule your "private" visit to the home and have the person meeting you arrested :)

Speaking of gurus guess who's back doing her usual crap:Karen HanoverI thought we saw the last of her when she got arrested by the FBI for impersonating them.

I do know that they have an arrest record which includes theft and possession - enough to know I don't want them in my property, but not enough to remove them legally.

How much would a repair bill be for someone pouring concrete down the toilet and what costitutes a tennant being arrested and thrown in jail for such damages?

It's like the biker who decides to walk onto the golf course and relieve himself in front of a bunch of beret & pink green knit cardigan-wearing country clubbers who stomp around and hollar about how "tough" they are, he's going to be arrested, this is an outrage, some people....

Have a small monetary reward for tenants that report suspicious activity that leads to an arrest etc.