Wow! Nice work. I had the exact same idea awhile back and even started on a prototype version of it. Really happy (and a bit jealous) to see it done so well.

Some of the things that I thought would be good:
Auto-complete (with a drop-down box) for the search box is a really nice way to search a restricted domain like movie names. This reference was useful for me: http://www.webreference.com/programming/javascript/ncz/colum...
Although the search result page is good so need to find a balance between directing to the actual movie page and the search page.

Combined lists with other users was the main focus I had when I was playing with this. Good to make it more obvious that inviting your friends allows you to do this. The example in your blog explains this well.

More lists of movies in the Discover Movies page. The people/genre lists are great but there are a lot more possibilities. Examples: All Academy award winners (by category), Box Office Top 10, Top Grossing Movies of all time, Top movies from other Ratings sites. I think people like to be able to tick off a complete list of something.

Adding to the list idea, have custom lists created by users. This would be a good viral idea for sharing via Facebook ex. Joe's Top 10 Worst Movies of All Time! How many have you seen?

Make these list pages as linkable as possible (not just on Facebook) as it will help with ranking on the search engines.

The viral strategy is a very good approach, but good to have multiple approaches. More link-worthy pages = more links = better search engine rankings.
One more example, make it very, very easy for people to add a link to their profile on their blogs etc. There was also a post here just the other day about startup sites to submit to. Try that as well.

Some options for sorting or re-arranging the movies would be nice.

bl4k mentioned affiliate links as a good revenue source. One other possibility would be to pay for privacy so that you can keep your profile private.

I found that there are lots of movies that I have seen that I want to see again. I know that adding this concept complicates the UI but if you find a nice way to do it it would be useful.

Include the year after the movie title on the hover overlay.

I was reluctant to log in using Facebook because I didn't want to post all the movies to my profile. Might be good to include some more clarification about what you do with a users profile (and the email address you need to provide). I'm sure this would increase the sign up rate.

Are there any issues with using TMDB for some of the data? It might not be an issue now but could become an issue if you get more popular.

Not sure if some of the pages already include this but a recommended list based on selecting popular movies from other users who have seen similar movies to you.

Add a link to a movie trailer site

I really like the implementation of "I dont want to see this movie". Good how you just add it on the Discover page and not the individual movie page.

Add affiliate links to Netflix sooner rather than later. It's useful for users and gives you a good idea how much revenue you can earn with little effort.

Keep up the great work! Would be great to see a first x months stats post on Hacker News sometime soon.