Is XML over Sockets good or bad pratice?

[Flamesofhell]

I've been working on a system that transmits xml over sockets for a while now. And i never really understood whats the real advantage of the choice of xml over sockets instead of a custom protocol. But i do see a lot of developers(specially originally web-developers) setting up this sort of implementation(xml over sockets). I do understand that is more "human-readable" (that's what i keep hearing). But,

• Xml carries an awful amount of characters, leading to huge messages when in fact the content is really small and simple.
• Message size varies, therefore you need to guarantee that you terminate your message with specific character or string pattern.
• There is more overhead when parsing xml

For all this reasons i remain skeptic about considering XML over Sockets for new systems when i could set my systems using a custom protocol using fixed-size messages. Avoiding huge messages being transmitted and performance hits parsing xml on the client size. Am i wrong to think as such ? What's "best" in terms of system-architecture ? Regards