We've seen a couple other examples of collaborative art, including Drawball Collaborative Graffiti Online and the One Million Masterpiece. The difference with the You Draw Poster, is that you can actually purchase this piece of collaborative art for your home!
The You Draw Poster is a humanities project which aims to produce a book of 50,000 individual drawings submitted online by members of the population. The site web owners proclaim that these, "Three fantastically rich and diverse posters that will keep you scrutinizing for ages. A celebration of the milestones of one hundred, two hundred and three hundred thousand drawings posted on Youdraw. A salute to the tens of thousands of artists that are helping build this collective project".
By becoming the happy owner of a poster you will contribute to keeping the Youdraw project alive and well. Plus, it only costs $17.