We have been using the XMPP transport with wildcard domain set for plugin.gateay.xmpp.connecthost so users can connect to any XMPP server through our transport.
Our server has been showing heavy load until we turned the XMPP transport off. There seems to be some possible loopback problem when users try to connect to an account on the same Openfire server using the transport. (see http://www.igniterealtime.org/community/thread/33508?tstart=0)
The most obvious problem would be someone connecting to the same account that the transport is on. There should be a way of preventing such connections. Does the gateway already check for loopbacks?