FYI: IMDb ratings database is public, you just need to download ftp://ftp.funet.fi/pub/mirrors/ftp.imdb.com/pub/ratings.list.gz file every week.

You can even apply diffs retroactively (I think) to get older ratings:

ftp://ftp.funet.fi/pub/mirrors/ftp.imdb.com/pub/diffs/

(via http://www.imdb.com/interfaces)