If God exists why doesnt he prove it?

Ive just been doing some preperation for my lunchbar at Liverpool in just over a weeks time. Ive been thinking through how to approach the subject recently and trying to get my head round this question. So as you do i started to draw a spider diagram to put my ideas down about how people think God would appear if he did. It was an amazing experience as i sat down and brainstormed and all the reasons i gave had biblical answers and came down to Jesus!! So i thought id scan it in and attatch it to my blog.
It would be great if people could add to this diagram by adding comments on the same question or anyways in which my thoughts have been wrong. Hope it all makes sense too!