I'm not sure how many movie fans know this, but in addition to all those movies you can download illegally, and the movies you can pay to download from iTunes, you can also stream and download hundreds of movies absolutely free, with no fear or legal consequences. It's a little complicated as to how this happened, but these movies are considered to be in the "public domain," which basically means that their copyright has expired and was never renewed. This is very common for early movies made before 1923, and a little less common for movies after that, and nearly nonexistent for recent movies; copyrights received today extend -- apparently -- for 95 years.
Public domain is always in flux. Famously, Frank Capra's 'It's a Wonderful Life' (1946) was once in the public domain, which led to its being shown on television hundreds of times during the holiday season, on various different channels. Eventually someone discovered that the film's musical score was still under copyright, and now it has been scaled back to a once-a-year event showing.