Luc De Brouwer has a reminder for web services developers out there - don't forget about backwards compatibility.
About a year ago I was asked by a client to update their existing web service because of some changes in the way they wanted to process their sales data. Luckily this client has always understood the importance of a Service-Oriented Architecture ( SOA ) since they deal with large amounts of resellers who need to access, edit and create data. All I had to do was apply the changes to their web service.
He lists the steps he followed when making the update - thinking about backwards compatibility, evaluating current functionality for use and possibly decommissioning older pieces.