I read the first Twilight book and couldn't stomach it anymore because it was so juvenile (yes, I realize it is "young adult", but thought that with so many adults reading it it might be better) and poorly written. I couldn't even try with the 50 Shades of Grey.
Ultimately, though, the author didn't HAVE to be a good writer. She was writing cheap knock-off fan-fic and it happened to take off. Had I been in her position, I would have taken advantage, too. The characters were never intended to be stand-alones (they were based off of already existing characters and only existed for the purpose of the sexual fantasy fan-fic), so they filled the roles for which they were intended. I don't know if anyone has read other fan fiction, but most of it is comparable to 50 shades of Grey in terms of style, character development (none) and storytelling. In other words, while there is some worthwhile writing, as a genre fan fiction mostly stinks and 50 Shades of Grey is no exception.
I would hope that no one would take ANY romance/erotica/sex novel seriously enough to base one's life off of. To be honest, MOST "romance" novels in book stores have overpowering "alpha males" and women who ultimately are submissive in the end. Few of them provide healthy templates for any kind of relationship.
I guess I am more disappointed that such poor, poor writing became so popular. It is mind-boggling, and makes me believe that any giddy, over-sexed teenaged girl (which is how the writing comes across, despite the author not fitting the criteria) could become a publishing sensation.