This question may be best answered by a question to you:
Would your business and perhaps your industry regulators (SOX, HIPAA, GLB) be pleased if one or more of your employees set an Outlook rule to auto-forward all their e-mail to your chief competitors? How about if each internal message was mirrored to a purchaser of identity theft-related information in exchange for cash payments?
Perhaps this is unlikely, possibly you have no corporate secrets or maybe none of your workers would behave in such a way. Trouble is, if you enable the technology, what's to stop someone from misusing it? Would you want to discover it after the fact or once it became a headline?
I can't tell you the right answer but I can tell you that it all depends on the nature of your business, your security policies and your viewpoint.
Best of luck
JM