Pros:

• Fast. Instant messages (IMs) appear on the recipient's screen as soon as you send them. 

• Free. Most services are completely free. The only catch is that you have no control over who your employees communicate with, so their conversations may not be limited to business. You can purchase interoffice-only messaging software, but they can be quite expensive.

• Attention-Getting. IMs pop up on your screen over the rest of your open files. It can be a great way of catching someone's attention while they're on the phone or in a meeting. You can, however, set most services to minimize messages so they alert you they've arrived but don't override your screen.

• Convenient. Send quick questions/answers without walking to another person's office or having to call them. It can be great for getting someone's attention when there's no time to wait for them to open their e-mail or check their voicemail. 

• Group Chats. Talk to more than one person at a time. This is a great feature if you need to have a conversation with several people in various offices but don't have the time to set up a phone, video or in-person meeting. 

• Minimal Space Needed. Most programs are very small and won't take up much space on your hard drive. 

Cons:

• Be Careful - It's Addictive. As AOL's Instant Messenger site says, it's "fast, simple and totally addictive." If your employees are overusing the service for personal use, it could get in the way of productivity. 

• Both Parties Need To Have The Software. While just about anyone can receive an IM, each party needs to have the same service to communicate with each other. 

• No Control Over Who Employees Talk To. Instant messages can be big time savers for businesses, but you can't limit "buddy lists" to just business. Like e-mail, there is huge potential for personal use.

• No Archives. Unlike e-mail, there is no way to save old messages.  This can make it harder to clarify

  Good ol' LBJ was actually quite paranoid about his correspondence, often writing "burn this" on personal letters.

   communications between employees, and almost impossible to track how they're using the service.

• Not Necessarily Secure. This lack of a trail also poses possible problems for company security as there is no firewall to block potentially infected files, and no way to monitor the communication of proprietary information. 

• Distracting. Some schools of thought hold that instant messaging can also interrupt general concentration. Most people check their e-mail at particular times, but instant messaging is constant. This can be dealt with in part, however, by setting messages to be minimized or by using a program that can still receive messages in the inbox even when it's turned off.

• Economy Model. Free instant messengers are popping up all over the place. But you have virtually no control over how they're being used in your office. 

• Luxury Model. Alternatively, you can purchase packages that provide extensive capabilities and management features. But they can be expensive, and there's still no guarantee your staff isn't using free instant messengers in addition.