As a 28-year Michigander (Flint/Detroit area), I don't think the left turning mechanism is responsible for any neighborhood divides...you could say that the divided highway contributes to this, but I am more inclined to blame "White Flight" (http://en.wikipedia.org/wiki/White_flight).
On the other hand, when faced with a blank text box, some more technical users will type in Markdown out of habit. Adding basic Markdown support while also having a couple buttons for bold/italics/link is an easy way to support both audiences.
How about, in addition to helping people track the movies they watch, you display information about which directors/actors/etc they seem to like best (based on the movies they have `liked', of course...)
Also, after clicking through about 50 movies on the `Discover Movies' page, I had `The Usual Suspects' show up about 15 times in a row on the page. Don't get me wrong, I love the movie, just figured I'd submit this particular behavior as a bug...:p