When I used your search criteria on a group I belong to, in Yahoo groups, it took me to the main page of the group....on yahoo. After actually going to the same group page, the normal way, I can say that the page is/was definately the current and up to date page. Plus it wasn't a cashed page.
I had to sign out of yahoo completely and then went back into this group from google, and it treated me just like a normal visitor to the site.
Except for the harvesting of email addies, which can be done much easier ways, I don't see any problem with google listing the site.