Palo Alto Networks, a company specializing in enterprise network products, summarized application traffic assessments for 20 large organizations — representing the behavior of over 350,000 users, and came to some interesting conclusions. It appears that enterprises have largely given up on controlling the use of IM, and existing policies, if any, are largely ignored.
Below is a chart from page 7 of the source report. Now, the data appears to be computed by site level, I thought the relative popularity of various IM apps was interesting.
[Source: The Application Usage and Risk Report]
Palo Alto Networks prides itself in providing strong visibility and policy-based control over applications running off enterprise networks.