Allow NON-Authenticated X11 Connections - How insecure/secure?

Hi,

How secure (or insecure) is it to NOT require X11 Authentication but
DO use ssh/X Forwarding?

I have an application which works a lot easier if X11 Authentication
is disabled, though I'm still using ssh w. X11 Forwarding.
But would like to get an idea of the risks.

Thanks,
Jon