[Alberta's Child]

I knew someone would chastise me for leaving Sam off that list!

I deliberately left him off because I believe he was protected from the Ring by his relative ignorance and immaturity (though these may not be the right words to use). In the context of the Ring, I viewed Sam as being similar to a very young child who, due to age and innocence, is not capable of knowingly doing something truly evil.

[Anitius Severinus Boethius]

As I said, I think the ring rejected him because of his goodness and purity and so he didn't feel the intense reluctance to give the ring up like the other ring-bearers felt.