Far too often do you find a movie (usually a somewhat recent release) that's just flat out terrible despite having a > 7 score on IMDB (and usually a Metacritic score in the 30's or 40's)
Example: "Spy Kids" got a 93% fresh rating from critics, but 45% from audience ratings.
Code attached should you want to investigate for yourself.
If I had unlimited time and money I would create a new movie review site that fights corruption. I would have a phone app for doing the reviews and it would require taking a photograph of your ticket stub at the theater and uploading it for proof (w GPS tag). It is far too easy and anonymous to participate in these online movie ratings sites that have a large impact on people's decision making. I have more ideas for the review site if anyone wanted to discuss it further.
People who are motivated to see a movie early are the same people who are likely to enjoy that movie. This makes it natural for movies to get rated very highly when they are first released. That's just natural.
If you forced people to photograph their ticket stub, I believe this could make the problem worse: mainly people who particularly loved the movie (or thought it was significantly worthy of comment) would be motivated enough to do that. You'll just collect the IMdB's 10s and 1s.
I know many people use the IMdB for their own record-keeping. These people would stop doing that if there was an administrative barrier that made it less convenient than a paper equivalent, e.g. writing in an address book. I strongly believe this makes their votes neutral/genuine compared to other survey methods.
Even a basic trimmed statistic would find a much more accurate average. Lazy people leaving 10s and 1s would be removed or given a lower weighting.