Personally, I think one of me around is enough <img src="/images/graemlins/wink.gif" alt="" />
Seriously, I think without proper legistlation and laws governing the agencies doing this kind of work, it can be abused. The research I think is grand and if a duplicate heart can be made, transplanted, and save someones life, then that is wonderful as well. However, without regulations and laws, someone is going to do the wrong thing for fun and profit.
I wrote an article a while back on the difference between identical twins and cloning if you are interested.
Identical twins versus cloning