Ahh, Diplomacy. I love it and I hate it. It is a great game, elegant in its design, and really educational in what it shows about pre-WW1 Europe.
But, as any aficionado knows, you will have a hard time winning unless you lie. And you may have to lie to all of the other players in the game, at least once each. This, as they say, may cause some hurt feelings. Especially among casual friends. So, I have a rule with Diplomacy, either only play with complete strangers, or play with people who will shrug off the necessary bad behavior of the game.
Having said that - I came across a picture I had of a Diplomacy game that I hosted a number of years back, while working at a University research center (not the one I am at now). It was a great game, for the few (game) years that it lasted. Eventually people lost interest and stopped turning in orders, but it was good while it lasted . . .