Well, firstly, it does depend on the show itself. If the host is not on close terms with the guest, they would normally use '-san' with anyone just to be formal. Then there's cases where the host is more informal, so the host might just refer to the guest by their last names only (Bad Boys did that originally with all members during AKB0ji59fun). I haven't seen a case where a host has referred to Mariko with '-sama', but I know that Takamina's nickname for Mariko is 'Mariko-sama'.
Hi, this might be a bit far out but in AKB0ji59fun episode number 5, the host was calling out the names of the girls who was participating in the upcoming game and he only added -san to Shinoda's name. The other obvious instance was in the November 11 2006 episode of Music Fighter where the host repeatedly added -sama to Shinoda's name.
My theory is, they recognise Shinoda's greatness too
