Most firms have done this for a long time. (Score 4, Insightful)

I work at one of the large investment banks and instant messaging has become a large part of how traders do business. They communicate with people from other firms, quote prices, and even make trades. All of this is much more efficient and effective than email or even the phone. The recording of these communications is mostly there to settle disputes. If I quote a price to you over IM and you accept the trade is done, and if later you come back and dispute the price, there needs to be some way to settle it. This is the main reason phone calls and emails are all recorded and saved. It is a good deal for the banks, along for the SEC when investigations come up.