(For the HTML 5 app and possibly iPhone app in future)

http://docs.moodle.org/22/en/Enable_mobile_web_services#What_happens_when_the_service_is_enabled

Instead:
enable the xml-rpc protocol
allow the 'webservice/xmlrpc:use' capability for authenticated user role

Will be necessary:
enable the rest protocol
allow the 'webservice/rest:use' capability for authenticated user role