Customers have a right to know! Businesses that deal with the public -- i.e., restaurants, hotels, retail stores, etc. -- should be required to post notice at each location if that location employs any violent offenders, felons, parolees, and especially registered sex offenders. By law sex offenders must register with the community, but for the person just passing through or the uninformed at large, they have no way of knowing who is working where.
We as citizens have a right to know who is serving us. We have a right to know who that man is cleaning the bathroom our child is using, or that hotel worker with all those keys, or that woman working the fitting rooms...
Sexual harassment doesn't just happen to employees, it happens to customers too.