Loek Bakker makes an analogy, likening SOAP to SUVs.
Now the good thing about this analogy is that it holds a very clear lesson for when to use it: if you do not need the off-road capabilities or if you never flick the 4WD switch, probably you do not need an SUV. If you do not need the SOAP extension /WS-* possibilities or if you never make clever use of the SOAP header, probably you do not need SOAP services.
One might argue, though, that SUVs just create an illusion of being capable of off-road usage … if I needed one, I’d rather use a real off-road car than one that just resembles one.
I’d use a full suspension mountain bike and cut up the SUV the moment it got bumpy. While Landrovers can climb and do river crossings nicely, they lack the agility to do technical stuff and their centre of gravity is such that they can flip if you try and traverse the steep stuff.
The only time I’ve been overtaken by a motor vehicle on an offroad descent was in the french pyrenees, by farmers in an old renault van.