I really have no desire to insert my arm into another person, however I do find the fettish oddly fascinating.
What is the root of this particular sexual behaviour? Where does it stem from emotionally/mentallyl? Does it have to do with some kind of regression -- "climbing back into the womb" so-to-speak?
Anyway, I will say I know a few people who've tried it and they say it's kinky as hell.