Cracked.com: "And since mermaids don't have souls with which to enter the afterlife (at least according to Hans Christian Andersen), she has to do 300 years of good deeds in order to earn one, only every time a child cries, she has to do an extra day for each teardrop. (Old Yeller probably tacked on about 500,000 years alone)"

@TARINunit9: Sounds like the moral was "You'd better quit your crying, or the little mermaid will never go to heaven. You little bitch."

It's not really all that surprising that Disney changed the ending…