Get Off My Backstory

A few days ago I was on this fanfiction site and came across some of the reviews for the author. Most of the reviews were the standard "OMG this story rocks!" but there were a few that stood out. Several of the commenters were asking questions about the backstory. Questions that had nothing to do with the main characters of the story or even characters of the series. I thought this was funny as heck and laughed about it for a good three minutes. I mean, come on, it's just FANFICTION! Then I had a thought (which is both dangerous and rare), if people react like this to fanfiction, what will they do with my work?

Do I risk having a reader question me about my backstory? If my character Liz suggests eating somewhere other than Popeye's Chicken and I've mention in the story that she hates Popeye's after getting some bad chicken there once. Will some nutcase email me with questions like "How many other people got sick that day"; "Was it some sort of conspiracy"; and "Did all the victims file a class action lawsuit and win"? Especially since it has no relevance to the story whatsoever.

I understand the importance of backstory and all, but there can be too much. Too much backstory cuts into the main plot. So where do you draw the line in creating the backstory?