See Federal Protection for Labor Organizing . Workplace acquaintances may become bitter enemies, or worse. A bitter atmosphere may be fostered. Anyone from any company can access any other companies posting area. Management and executives can literally 'get into the minds' of their competition's employees.
Heads roll at upper management.
More room up top. The companies will have no control over the postings. The Webmaster can not be bought for any dollar amount. No matter how popular a WPL has become to the employees of any workplace, the site remains up and running to the best of the Web master's abilities. The web site has multiple hosts to ensure that an Internet Service Provider going out of business, will not affect the maintenance of this site.