The partition between work and home has been broken, which means every busy professional should have a personal assistant, not a corporate secretary.
Especially in professional services firms, I think there is a big opportunity for efficiency savings because many busy bosses still use a secretary in the conventional sense (which gives him/her plenty of time for crossword puzzels during the day). A secretary used to spend time mailing documents, obtain driving directions, and so forth. All of this is now automated with email and the web. It’s still acceptable for someone to call "on behalf of Mr. Smith," but is it acceptable to "email on behalf on Mr. Smith"? After all, sending a quick email only takes 30 seconds, so many bosses choose not to lose the personal touch. These are all new challenges.
My take is that the era of traditional "corporate secretaries" is over and that any busy person who needs support should have a "personal assistant." What’s the difference? A personal assistant aids the professional in both personal and business stuff. It should not be weird for the CEO to ask his secretary to call his son’s baseball coach and confirm the time of the game. A personal assistant doesn’t need to travel with the CEO like an entourage would, but as the CEO can now complete tasks the secretary used to do in a more efficient manner, the personal assistant should use that excess time to make the CEO more successful and productive in his personal life.