ACM Queue has two articles on Instant Messengers (IM); the first article deals with what a study found after looking over chat transcripts from 2000 to 2001.  Here's a snippet:

"...When we analyzed what people were using instant messages to accomplish, we discovered several interesting findings, namely:

• Although a common impression of IM is that it's used primarily for simple questions and quick clarifications, we found that was true only about 28 percent of the time.
  
• Despite the perception that IM is commonly used for social purposes in the workplace, we found that was rarely the case. Only 13 percent of the conversations we monitored included any personal topics whatsoever, and only 6.4 percent were exclusively personal.
  
• Concerns that IM might distract people from their work proved to be unfounded. The majority of the workplace IM conversations we observed, 62 percent, focused entirely on work-related matters."

My personal experience is to the contrary; I'm a little suspect of the chat transcripts - I think some people might have been aware they were being monitored ;)

The second article is a study by AT&T on what they figure we might see in IMs, citing "awareness services".