More info:

http://www.ehow.com/list_5794056_disadvantages-blackberry-phone.html

A major setback to the BlackBerry when used for business is constant access to work. At first, receiving and sending work-related emails seems convenient and efficient in communicating with your boss, customers or co-workers. However, when you begin the habit of quick replies on vacations or weekends, the BlackBerry may become your ball and chain. Your boss and co-workers will acclimate to constant communication, and suddenly ignoring company emails can have negative effects. This is especially true if your BlackBerry is provided by an employer with demanding deadlines.