Sleeping with the Enemy

I went to a Hyundai show room last week to look for a new car for my mother. The salesman asked me what car I drove, and I said I drive a Suzuki Baleno. Surprisingly, he said he also drove a Baleno and found the car to be very good. He added that another of his colleagues in the same showroom also drove a Suzuki Baleno.
One of the classic dilemmas in Business Ethics is whether it is ethical for a company's employee to use products of a competitor, and on the other hand can companies insist that employees avoid such behaviour. Fortunately, this is one of the more light-hearted BE dilemmas and quite interesting to delve in. Let us look at a few scenarios.
Can a Toyota salesperson be seen driving a Honda Civic? Can a Philips manager have a Sony Plasma TV in her drawing room? These are visible demonstrations, and hence one can argue that they are potentially more harmful to the brands that they work for. What then about usage that is less visible, like a P&G Marketing Manager using Colgate tooth paste in his bathroom, or a Mr Turner working for Microsoft having a personal email account id called turncoat@gmail.com? Or the mother of all offences - a Coke manager drinking Pepsi while watering her garden? Is visible consumption of competitor products a greater sin than less visible ones? There is of course a third dimension that seems acceptable - which is the use of a competitor product to check it out - like a Lufthansa sales executive flying BA to check out if his company is giving away too much legroom compared to the British airline.
And can companies prohibit or discourage employees from using competitor products?
There are no easy answers to these questions, and in my experience I have not seen any formal policies on these aspects. The accepted position seems that companies do not have a right to prevent employees from being customers of a competitor, as it would be seen as interfering with their fundamental rights. This sounds rather unfair on the companies, but is the expected stance from an ethical organisation.
Unfortunately, most discussions on BE focus on the responsibilities of the organisation towards its stakeholders, with limited discussion on the reverse. In my view, an employee should not be using a competitor's product if it is going to lead to a clear conflict of interest that in turn is likely to harm the company's reputation. Like the Hyundai salesman driving around in a Suzuki. And I also feel senior managers of a company should not be using competitor products as they are seen by the outside world to be representing what the company stands for. This may sound old-fashioned, but in the olden days these were unwritten rules that everyone followed.
Of course I would be less worried if a Pepsi shop floor worker drinks Coke while on vacation, or a Sony clerk buys a Samsung handycam as it is 30% cheaper. Having a lower-paying job has its advantages sometimes, and freedom of choice may be one of them!