I think David's idea is a cool one. Probably would want it turned off by default. In the case of a site like GP they'd probably get overwhelmed by people offering to redo it in Zope, IBM Websphere, RedHat CCS, etc etc. Folks like GP get pings like this anyway, though, so I kinda doubt it would be increased. They're already known to be an OpenACS 4 site in the community and anyone reading here can feel free.
So I doubt in practice there'd be a significant effect.
Anyway ... turned off by default? Maybe a link on the default index page for the site if turned on. Why not? The default index page never survives customization anyway ... so our OpenACS community members could access via the "secret" URL (just as I do here to reach the site membership page at https://openacs.org/directory, not really a "secret", just not linked from anywhere and I keep forgetting to add it).
