I work in physical trading and use yahoo on a daily basis to trade swaps, execute physical deals, and chat with customers. If yahoo were to drop support unexpectedly, there would be a pretty large problem.

We have already been briefed by our IT departments that we are moving to another service with the front end being one of the following - IceChat(from the ICE exchange), Reuters, Bloomberg, Trillian. Although Yahoo will be the back-end in protocol sense, I believe that will be phased out once the trade migrates to another service.

It's a bigger problem than most imagine and can't be executed at a drop of a hat due to legal compliance in logging all communications in the case something went awry or other similar situations.