Hide "Assignee" from certain user groups

We sometimes dont want our customers to see who is actually working on what item, as some bad customers then tend to talk directly to the developers (which is in many cases not very good) and overgo the project lead, which he is supposed to talk to.

What i would propose is a new permission in the permission sheme, called "Sees Assignee".

As an alternative you could couple this permission together with the permission to assign someone.