I have set up Moodle so that I can have different companies using the system without each knowing of the others existence on the system, with 2 exceptions. The first is the most worrying: if a person from Company A  clicks on 'site home' a button appears under the course description called 'All Courses' and it does what it says, it lists all courses showing the names of the other companies, because the courses are named after the company name. The other way you can see a list of courses is simply by logging in as a guest. Your thoughts, contributions and (most of all) solutions, are most welcome.