Transaction Integrity with Connected Systems: Recently Vjekoslav Babic wrote about this subject on his Navigate into Success blog.
"With .NET Interoperability around, it's very likely you'll be synchronously calling external web services from C/AL, to exchange data. I won't go into discussing whether or not this kind of architecture is good (my own position is that it isn't), you may end up having situations where your C/AL code simply makes a synchronous call to external systems, such as web services.
Any external call is an expected point of failure. An important question you must always have in mind when calling external functions is transaction integrity. ...