If you want to get information about a group, do not content yourself with Google. You can find some helpful stuff quite often if you go further and search the various Google groups and listserves.
One trend I noted in the listserve material is that Hoffman Quadrinity has been marketed to troubled families. If it is not based on tested and researched protocols that meet current standards of care as defined by professional family therapists and is indeed, just another money maker--thats bad news.
Here are some things from the listserve:
A list of groups NOT recommended by a German watchdog agency:
A comment by a person who claimed to note similarities between Landmark Forum and Quadrinity: