The problem with information like this being publicly available is that some sex offenders will simply move without notifying the authorities. So instead of knowing where most sex offenders are, the publicity will mean that authorities will lose track of where some are. How many people would be tempted to go and beat the shit out of local sex offenders, or generally make things as difficult as possible for them? That alone would be a good reason for them wanting to move somewhere where people don't know their past. Registered sex offenders have to live somewhere. Surely it is better if the authorities know where they are and can keep track of their activities, rather than them going into hiding or "disappearing" by moving to a different state with nobody knowing? Obviously people would be concerned if a sex offender was living in their area. But as others have highlighted, just knowing the name and address is worse than knowing nothing. You would also need to know the details to form an opinion as to whether they were really a risk. For example "had sex with a 17 year old when 18" would be virtually no risk whereas "sexually abused numerous young children over several years" is a much higher risk. But such information is probably unavailable due to privacy reasons. So we have a situation where a little information is more dangerous than no information or full information.
