Just look at this article.
Birgit Loch and Christine McDonald provide the results of a pilot study that explored how a free and widely available chat client (MSN Messenger) could serve as a viable medium for distance learning tutorials in mathematics.
By providing its users with an easy way to incorporate diagrams, symbols, and specialized mathematical annotations in their communications, this popular chat client offers a convenient alternative to the whiteboard function of Blackboard and other proprietary systems.
Source: Innovate