Zscaler provide a cloud browsing solution. The web traffic is “clean” against malware, virus, and also policy define by yours own internal rules.
Filtering and categorization is also performing on https site, by setup a trusted authority on computer. Web 2.0 can be monitor but it's in option.
User database can be done by AD synchronization, open LDAP, or Zscaler can store a local database. The authentication method is providing by a cookie flash store in the local user folder (compatible with profile store on share or Vdesk). The password policy can be hardness as your internal policy.
Remote user can also use Zscaler at home, and use the same restriction &protection anywhere.
The real force of this solution is to provide a fail over on their gateway by DNS mechanism, and the datacenter around the world.
The reporting is managed on global console so international company can have data from every user from every location. The reporting can be done by internet gateway (location), departement (sales, IT, …) or per user.
The competitors of this solution are Messagelabs, scansafe (cisco), webroot and websense.