I have heard this argument before, but to me, it can be superb training, teaching one to see everthing quickly and run through combinations with the eyes more than the brain etc.
Is Quick Chess Bad for You ?
You can make some use of quick chess to help you in more traditional time periods. Quick chess is a great way to get a lot of games played to see how an opening flows and what endgames tend to result. Basicly it is a good way for you to see the forest before delving into the trees themselves.

Check out Dan Heisman's website (www.danheisman.com), he's a Master and an online chess coach who talks a lot about using all of your time and making the best move possible in the time you have available. After reading several of his columns I totally stopped playing blitz. He emphasizes that you become better by playing slowly, and that good blitz players got that way by becoming good slow players.
Think about how you play blitz, is there any thinking or analysis going on, or is it just reaction? Once you've done the thinking and analysis slowly, then you can gain speed, but you must take the time to do the thinking at least once.
On the other hand, he also emphasizes that it is the clock that makes chess a sport and not just a diversion. Many good players can excel if they have unlimited time, but only the really good can do it with a time limition.

Thanks Jeremy, some very good points made. Walk before you can run. I will check out that website.
I'm still wondering if BLitz and Quick games are even "real" chess at all ? Is there a blitz world championship ? How can it be good Chess if you are just reacting quickly instead of thinking through some good strategies ?

There is a blitz world championship - I think Anand is the champion of that as well. He's certainly thought of as one of the strongest fast players around (along with Nakamura).

Most chess teachers instruct that blitz chess is imperative to one's chess learning but only in moderate doses. It helps you with your time management, decision making, pattern recognition as well as allowing you to practice new lines and openings you might be hesitant to test in a longer game (as others already stated). It quickens the process of experimentation which in many cases is key to learning BUT if you play too much without balancing it out with slower games then I think it does hurt your chess.
On a sidenote 99% of the grandmasters and international masters that play on another site ive checked out are all for the most part phenomenal at blitz so I think it can be a key aspect of a strong player's arsenal. Then again I guess it can also be deduced that they are good at blitz because they are good at slow chess. I don't know.

Actually Ivanchuk is the Blitz World Champion, he beat Anand with black in the final game of the tournament last year. There's another one coming up this year.

I'd rather play blitz than slow chess.
I don't like memorizing openings, so until something like Fisher Chess develops, I'll stick to blitz, where strategic thinking is stronger than memorizing.

I don't like playing blitz that much, but I also don't like playing under time pressure. As long as you don't play like a blitz player in a long game (which is what players generally think playing blitz does) it can be a huge help because it can be important to make quick decisions or calculations when you have to.

I myself consider "real chess" to be slow/classic chess at standard time controls. I see blitz and quick/rapid chess as variants of chess, not real chess. Its true that the best blitz players in the world are also top players in "slow chess" . There are exceptions I guess, I have read that Botvinnik wasnt good at blitz and cared nothing for it.

I also remember that Bronstein said it was important to practice blitz to prepare for situations when you're in time trouble, to echo a point made above.
And I think there is value in seeing quickly a lot of common positions and errors, but I think it would also be important that the blitz opponent be good enough to always punish a bad move, and not just move randomly themselves. But at my level (rather low) I think I can gain the most from taking my time most of the time.

I like fast chess. Not to much thinking just moving. The problem is that I make more mistakes. Another problem is that when I'm playing blitz or long chess I often play to fast. (like fast chess)
I believe that Fischer advocated speed chess. It is an excellent way to learn many different types of positions. One important thing is that if you are playing a long game you are reluctant to try different things because who wants to be tortured for a couple of hours in a shitty position. You can play at least 6 speed chess games an hour. Also if you are prone to time trouble then you have an extra weapon in regular OTB tourneys. I have had to make 10 moves in a minute or so before and I believe that speed chess helped me.(I once drew a game which I should have lost because my opponent tried to take advantage of my time trouble}. Also if you are playing someone significantly stronger or weaker you can give time odds. For instance, I had a room-mate named Tom O'Donnell(2500 CFC) and we played all the time at 5-1 odds. It taught me alot about chess. Hope this is helpful.

thanks escral, I have actually quit playing live chess altogether...I can't seem to win a fast game no matter what I do....I don't understand it....

In quick chess, we tend to not think and play the "obvious move" which comes to mind. The "obvious move" is sometimes a bad move. Although not punished in quick chess so much, playing the obvious move can lead to swift punishment in long, more traditional chess games. Also, my game seems to suffer when I play this type of chess.
Long chess is, in my opinion, the only real way to play chess. I'm not putting blitz down or anything, but certainly lightning... "Let's make as many random senseless moves as we can in under a minute!". As aforementioned, Blitz is usefull, but Lightning... not at all. With long chess, you use your brain much much more, and you have time to look through all the variants of a move, not just immediate consequences.
I've been wondering about this so I thought I would put it up for discussion.
It seems when I play alot of "quick" games on live chess, my regular game suffers.
I'm wondering what benefit, if any, quick chess adds to your overall game ?
My thought is that it is actually bad for you, forces you to move quickly and carelessly, is it even considered "real" Chess ??