I do a lot of business over instant messaging. Often, these chat sessions have important information that I need later. I used to copy out any important info into a separate file, but now many of the chat clients let you log your instant messaging. Some operating systems make it easy to search through your chat sessions to find a bit of information when you need it.
If you use the web version of Google’s chat product that is integrated with Gmail, you can set it to record your chats and make them available when you search your email. The box to change this is under the chat tab in the settings: