This new rule was born out of the failed card check legislation and it basically allows unions to intimidate employees into joining by giving them access to every worker’s private home address and phone number:
But now under this new rule making, if a business is petitioned to form a union, within 2 days they would have to turn over the home address, email address, and home telephone number of every employee and that would go directly to the union. And then if they want to pay you a visit or call you at home, they can.
(via BBTV)