When someone tells me they play the lottery for entertainment, I lose a serious amount of respect for them. There's being irrational, and then there's understanding exactly how your irrationality is being exploited and just going along with it!

The negative expected value in dollars is enough by itself, but the "how happy will I be?" calculations are even more depressingly bad. The utility of money is usually measured on a log scale, because your first thousand dollars does a lot more for your happiness than your first ten thousand. By that measure going from ten thousand dollars in the bank to ten million wouldn't make you a thousand times happier, it would make you twice as happy. At least until you get used to it (see: Hedonic treadmill [1]). There's a surprising number of bankruptcies caused by lottery winniners, too [1]. Also the whole stressed friendship thing.

So... yeah, playing the lottery gets you negative respect from me and I think that's justified.

1: http://en.wikipedia.org/wiki/Hedonic_treadmill 2: http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1324845##