How much SHOULD you let other writers influence you?

Clearly you don’t want to give up your own idea of a story in order to accommodate another writer’s idea.  If you’re willing to do that then you might as well go around doing all the stories that non-writers perpetually offer to writers. “You know what you should write?  You should write about my grandfather <or other relative, friend, favorite pet, or self> who <insert long boring monolog>.” 
But it really helps to get some feedback, and sometimes that feedback can take a story in a different direction than I had originally thought, ways that I like.

So where do you draw the line?

Alice