CU Psychology and Neuroscience Professor and Chair Leaf Van Boven (Social) was interviewed for an article in Colorado Arts and Sciences Magazine about why people play the lottery given the very (very) low probability that they'll actually win. A confluence of factors are at play, including people overestimating the odds that they'll win, and also not taking into account the negative emotions they'll feel if they don't play. Read the A&S Magazine article, which has links to earlier research on the topic.