Most common methods of sourcing new members

On his Membership Marketing blog Tony Rossell recently talked about how research has found direct mail to be the most common method of sourcing new members (see: Direct mail is tops for membership). Here is where the Australian, UK and US markets seem to be quite different. In Australia and the UK traditional professional associations and industry bodies have rarely used direct mail to its full potential. Is there an opportunity here we are missing? If you've had any experience with direct mail please comment below. I'd love to hear what you have to say.