I think it depends on the child. I moved my son out of his crib when he was 2 years old, he was starting to crawl out of his crib, and always wanted to sleep in my bed, because it was a "big bed". So, I went and got him his very own "big bed".
I do think 1 and a half and younger though is too young, because you then risk more falls, accidents, etc. You should make sure you will hear your child wake, and that your child will come to you or the bathroom first. Be careful of stairs, windows, etc.
Good luck.