I think that MOST people really have no idea what-so-ever how real cloning tech works. Many of the things that people worry about are really not possible, and really are created by hollywood. Or if they are possible they wont be allowed.
As for my views, i believe that humanity would be.. to put it bluntly, stupid beyond any possible description with the use of language, if we do NOT take advantage of cloning. The benefits will VASTLY out-weight any and all negative aspects.
Replacement organs would be producable by many many many means. Produced in liquid suspenson by themselves, grown in a headless husk (human or animal), or grown within other living animals such as pigs. (i mean.. we EAT them.. we slaughter THOUSANDS of them on a DAILY basis... how is this any worse.. it helps sustain us. Hell.. after you get your heart/lung/liver/spleen/urethra transplant from that pig that was growing a new part for you you can have it for dinner) These are very few of the almost infinite number of ways to do it. THEY DO NOT ALL HAVE TO BE EVIL.
Stem cell tech could produce the ability to grow entire organs or body parts inside the person that requires them. Stem cells are basically cells that arent specified yet. This means they have not yet turned into a specific type of cell, such as a skin cell or a liver cell. Stem cells could possibly, in time, be used to regenerate and repair damaged or lost anything from skin to organs to limbs. It could possibly be used to fight and eradicate cancer. It could cure and eradicate diseases like parkinson's disease, or diabetes, as well as COUNTLESS other diseases and sicknesses that have plagued our species, and others, for as long as we have existed.
And before anyone gets all upset about stem cells coming from fetuses.. well they are also found on places in the human body in a born human. For example, they can be found beneath teeth.. like when a child is growing their teeth. Although im not against using aborted fetuses to produce results. The child has already been torn from it's mother's womb and brutally slaughtered... we can atleast give the child SOME purpose for his/her life (all-be-it extremely short) and that is to save lives.. what would be more appropriate. Its either that or, quite literally, thrown in the garbage, or incinerated... what a waste.
DNA research can cure *DEATH BY OLD AGE*. Not only would you not die of old age.. but you would not age past a certain point. That means you *could* live to be 100+ and NOT LOOK like you are 100+. In fact you will look like you would in your prime... possibly even better depending on how well you take care of yourself. You would still die by other means, such as car accidents.. war.. natural disasters.. yet un-cured diseases/virii.. drug use.. brain damage/deterioration.
Death by old age is caused by.. well.. pretty much running out of usable cells. At the end of your double-helix DNA there is a "cap" of sorts, think of it as a lot of knots at the end of a braided rope. Every time a cell divides, your DNA divides along with it. Every time your DNA divides those "caps", called telomeres, shorten, causing your DNA to get closer and closer to "unraveling" as you get older. The older you get, the shorter they get, until you eventually start to run out of viable cells/DNA. Your body begins to deteriorate faster and faster until one day you just.. stop.
Certain parts of our bodies already produce the chemical (telomerase - a DNA polyerase) that extends these "caps". The problem is that it is produced in very small quantities and only in certain areas of the body in those small quantities. One of those places is skin. Since it is the largest organ of the body it requires the most DNA to keep it chuggin along.. grownin as normal.. healing those cuts and scrapes.. etc. Cloning technology can take advantage of telomerase by altering certain other parts of the body, such as vital organs (but not the brain) to produce it.. possibly helping to sustain their longevity.
As for over-population... whats the solution? Space travel/exploration/colonization. People laugh at that, but it is the INEVITABLE course for humanity if we dont obliterate ourselves before we attain it. The solar system is filled with planets and moons just waiting for us to take our rightful place in space. The solar system can sustain our expansion for a very long time. We would not need to travel outside of it for hundreds, possibly even thousands, of years. By the time we will need to, we will have advanced enough to do it.
To be absolutely honest, I'm rather pissed off that we have yet to expand our space program beyond the joke it is now. We have not even begun to CONSIDER scratching the surface of our potential in that frontier and i *can't stand* how this world is DRAGGING IT'S FEET on it.
In the end, people will still not live forever. People will always find a way to kill themselves and/or eachother. There will ALWAYS be death. There is no avoiding death. We MUST TAKE and HOLD life.. our lives.. for as long as we can.. it will never come again.