But then, Barry McGuire was also on the "TLIYL" program and they brought him back. And speaking of Barry, maybe I mis-heard this, but I thought I he stated in the introduction to "Greenback Dollar" that he wrote that song there at the Avalon Theater back in the '60's. That doesn't jive with my knowledge of the song's origins and it certainly isn't documented anywhere that I know of. Hoyt Axton and Ken Ramsey are credited with that song.
As for how the guests were chosen, my guess is that it had to do with financial considerations and logistics. Tom Guard would have had to fly in from the east coast, as would McGuinn. Judy Collins, Joan Baez, Bob Dylan and Paul Simon would have been too expensive to cast, I'm sure. Barry, Josh, Timothy B. (why was he there???), Al Jardine, Trini Lopez and the Limeliters are all in the S. Calif. area, so easily accessible probably.
All that said, it would be fun to see a show with current groups (Mumford & Sons, etc.) that were possibly influenced by the Trio. Another professed early Trio fan is Jimmy Buffet, but again - too far away and too expensive probably.
I'm still scratching my head over Sana Christian, tho. No connection whatsoever and no name value.