Custom url structure – pages under a custom post type

example.com/event/london-2012/speakers/john-doe

You need an “event” post type and a “speaker post type. The event post type should be hierarchical and should have a sub-page called “speakers” which should use a custom template that displays all the “speaker” post types assigned to that event (see the Posts 2 Posts plugin).

Then you can create other sub-pages like agenda, register, etc.