[a3_nm]

Not sure about the actual statistics, but XMPP is not just a standard for messaging between people: I think it's also intended as a backend technology for communication behind automated services. So even though there may not be many humans using XMPP as a messaging application, there may be many people who "use it" without noticing (as in, use a website, etc., which relies on XMPP somewhere).

[notyourwork]

I don't have experience with xmpp protocol but how is it better than an http or soap for example?

[SamWhited]

XMPP Core is a protocol at (roughly) the same level as HTTP: it provides basic semantics for sending and getting data, and you can build your own application level protocols on top of it. XMPP IM is an application level protocol built on top of it that does something specific (instant messaging). It could have been built on HTTP as well, but they were designed to work well together.

If we're comparing XMPP core to HTTP, the difference is that XMPP core is async and stateful (like instant messaging sessions) and HTTP is synchronous and stateless (great for fetching documents).

[icebraining]

HTTP and SOAP are generic, XMPP provides semantics for specific chat/IM related concepts like users, presence, user-to-user messages, etc.