A little late in calling attention to this, but the infamous fourth season of "Moonlighting" comes out on September 12. You may recall this as the year when a combination of Cybill Shepherd's pregnancy and a writers' strike led to a string of episodes where the two lead characters hardly ever appeared together, followed by the decision to marry Shepherd off to a new character she'd only just met -- the dumbest decision since, well, since Jack Scalia was added to the disastrous fifth season of "Remington Steele" the year before. (Odd how these comedy-romance-mystery shows tend to flame out in similar ways.)
There are two things to be noted about the implosion of "Moonlighting." One, despite the legend, it didn't really have all that much to do with David and Maddie finally sleeping together. The episode where they slept together wasn't even the season 3 finale; they followed it up with another episode that deftly addressed the question of whether the show could go on without the sexual tension, and concluded that their relationship was still messed-up enough to allow for more stories. What killed the show was the double-whammy of writing around the pregnancy followed by the universally-hated marriage storyline; but that was a result of bad luck and bad decision-making, not getting the characters together.
Which sort of leads in to the other thing to be noted: nobody ever says this directly on the DVD special features, but it's kind of painfully clear that Glenn Gordon Caron, in a sense, had no business running a show. Under normal circumstances, you would expect that a guy who can't deliver episodes on time or on budget, can't keep tempers from flaring up on the set, can't keep anything organized -- can't, in other words, fulfil the basic managerial duties of a showrunner -- would be fired. The problem was, of course, that Caron was bad at running a show (one writer called it "the worst-run show in the history of the cathode ray tube"), but good at writing and re-writing the show, and what's more, without him, there really couldn't be a show. So ABC, at least for the first four seasons, appears to have grudgingly accepted the trade-off of a badly-managed but well-written show. And of course in the fifth season, when Caron was forced out, the show deteriorated even more and got canceled.