Wow! I wish I would have seen this thread earlier as there is so much on which to comment, but I guess I will add my two cents into the debate of whether or not Mormonism falls within Christianity.
To be completely honest, I don't know enough about Mormon beliefs to answer it with 100% confidence, but I would say at this point no.
However, there is a distinction I would like to raise that I think is very important: while a doctrine of beliefs may by Christian, it does not follow that the people who claim to follow them are Christian; likewise, although a doctrine of beliefs may not be Christian, there may be Christians who claim to follow them.
What I am getting at here is that I think all who are Christian can agree that not all who attend our churches are Christian. There are Methodists, Anglicans, Serbian Orthodox, Presbyterians, Messianic Jews, Pentacostals, etc who all rightfully claim these label because of there church membership, but who are not Christian because they do not accept what t BuckeyeScot provided as a very nice statement of the defining issue of our identity:
Nevertheless, I can also speak from experience that in churches that have gone astray from the faith there are Christians. Take Catholicism in which I was raised. While I don't believe the Pope is antichrist or the Catholic Church is the Beast like some try to argue, I will state that it is one of the most polluted forms of Christianity in existence to the point where it is on the edge of losing its right to claim the title (official acceptance of Mary as co-reedemer, which is being considered, will be the final tipping point). However, I became a Christian within Catholicism and remained as such for 7 years before leaving it. I know many people who remain practicing Catholics whom if you speak with them about their faith, it becomes obvious they are Christians.
My current understanding of Mormonism is that as an official church it is not Christian for many of the reasons already given in this thread. Despite this, I do believe there are individuals within the Mormon faith who are Christians because their faith is defined by the quote from above.
Of course, the truly sad commentary about all of this is that there are so many denominations. Christianity was never meant to be so divided and it is testimony to 2000 years of man's traditions and teachings entering into those given to us by God. The profane has been mixed with the holy, and the result has become the sad history of Christians fighting are arguing against other Christians.