SOAP Disadvantages:
The SOAP specification contains no mention of security facilities.
SOAP 1.1 specification does not specify a default encoding for the message body. There is an encoding defined in the spec, but it is not required that you use this encoding to be compliant: Any custom encoding that you choose can be specified in the encodingStyle attribute of the message or of individual elements in the message.
Because SOAP deals with objects serialized to plain text and not with stringified remote object references (interoperable object references, IORs, as defined in CORBA), distributed garbage collection has no meaning.
SOAP clients do not hold any stateful references to remote objects.