In general, I think there's a lot more vigorous defense of trademarks and other intellectual property now than there had been in the past. "Everything" can now be "monetized" so "everything" needs to be "protected."
A non-GS example: The Union Pacific Railroad started painting the heralds of its predecessor lines on a few freight cars, so that they could say that the trademark was still in use and therefore remained their intellectual property. This prevented just anyone from using, say, the Missouri Pacific Railroad trademark on a model train, or a calendar, coffee mug, whatever. There was a huge flap over this with respect to licensing demands and eventually UP backed down at least in terms of model train royalties, but there's still a licensing agreement that has to be signed. UP isn't so nice with other items like calendars and T-shirts, as far as I know.
Getting back to GS, I can't imagine that Fallon et al wouldn't have approached Fremantle to get permission to do "Password." And they do a nice job as well. If it had been a one time "parody" then I could see them asking for forgiveness later.