Well, what would you do with them?
1-Leave them in prison forever (overcrowding, expensive)
2-Concrete shoes in the river (ethics?)
3-Lifetime on benefits (expense)
4-Send them back (or just up north)
Inevitably they're going to end up getting a job. If everybody decides to run them out of town, refuse to work with them, etc, you have to then choose an option from that list. Plus if they can't get a job they're going to be an increased risk of further offending.
So pretty much they have to get a job, and therefore someone has to work with them. I don't think it's therefore a good idea to allow every Tom, Dick and Harry to know be able to dig this information up. Should be restricted to employers and kept confidential. I'd previously assumed that was the case...