writing off a "business lunch": true?

[drhess]

Not having worked in a fancy business world where I would be in on such secrets, is it true that people can "write off" on their taxes business lunches? Hww does that work?

Separate question: What is the policy justification for that? (Not interested in a debate on the merits of the idea, just wondering where the idea came from or what its supposed to be related to, assuming that was once true or still is true).