[Incidentally; spoilers for said shows follow.]
American TV has always been ready to chop shows with little mercy, and in the days when each show was always a self contained story, this was much less of an issue. However, now many shows have epic, overarching storylines, and when a show like this gets the axe, it mostly never gets an ending to the story. Instead we are left dangling.
V ended with Anna giving her Bliss to the world, a trio of key deaths, another character in peril, and the introduction of a whole new aspect to the show in the shape of Project Aries. Its axing meant that Marc Singer's character, instead of being the important person he was destined to be is now a mere footnote to proceedings; little more than a fan-pleasing cameo.
The Event ended with the plan to unleash the virus thwarted, the array rather than just brining Sophia's people to Earth bringing the entire frickin' planet; and even with that brief last exchange between the president's wife and her son; "What is it mommy?", "Home" just made you ache for more.
FlashForward ended just as we actually got to the point of the first flash forward, with tantalising hints of the end of the world in a few years time.
And Heroes... although the main points of the season had been wrapped up - the carnival storyline, there was that tantalising moment at the end where Claire announces the existence of those with powers to the world...
You see, the trouble is that by the time a show gets word it's getting the axe, it's too late to give a conclusion. Both V and Heroes had already aired when they got the axe, with the other two getting the chop after filming had finished with just a couple of episodes to screen. This meant there was no way that any of the shows could have an ending. They just had to put up with what they had already got in the can. Moments intended as cliffhangers had to serve as cliffhangers.
In the case of all of these, they were pretty much gamechanging moments; however, in the end, they're now only gamechangers in the same way that Eric Cartman picking up his ball and hissing "Screw you guys, I'm going home" is to the kids' ball game.
I really can't help but wish that they'd all got the word of the axing earlier; that way last episodes could have been changed so that they were able to fashion an ending, even if a rushed one. That's not an unreasonable demand, is it?
I remember Quantum Leap ending; that last ever episode was just meant to be an end of season episode. But, with a small amount of overdubbing, and a couple of captions (which still manage to make me wonderfully happy, and depressingly sad at the same time) the show got an ending. But, that was an episodic, rather than a serial, show, and thus much easier to tweak at the last moment.
Lost spoilt us, I think; from the end of Season 3 we knew that there would definitely be just three more, shorter, seasons and then it would be The End. That meant they had the space to give the show the ending they wanted, and they wouldn't have to to either stretch out or unduly compress the ending.
And it really makes you wary of investing time in a new show, as you'll have it in the back of your mind that there'll be a chance that it won't last beyond 24-ish episodes, and be unresolved. Of next year's crop I'm looking forward to Alcatraz (with Jorge Garcia; there's a trailer already. It's great), and Person of Interest (with Michael Emerson). But part of me thinks I should wait until the end of the season to see if they get picked up at least for a second season. I just don't want the disappointment should one or the other get the axe with a whopping cliffhanger.
Of course, there is one inherent irony here; my favourite show remains Twin Peaks. A show that got axed after 30 episodes. And ends on a whopper of a cliffhanger. And they knew they were getting the axe in time to give the show an ending. But Lynch and Frost chose to end on that cliffhanger.