As long as employers can be held responsible for harassing e-mails, etc. via sexual harassment lawsuits, I’d have to side with the employers on this one. Plus, one needs to consider that the company e-mail and internet connects are company property. They should have the right to ensure these company assets are used for only authorized activities.
In a related area, does anyone know if employers are allowed to monitor and/or restrict telephone calls made by employees? Seems like some of the same issues can be applied there.