Some friends and I have been playing this way for a few years now, and hands down it is a better experience than using any of the cumbersome boards and having to manually adjudicate everything.
Submit one move every Tuesday, it's now a tradition.
Seeing other people walk off together to talk to each other.
Seeing others explode upon being backstabbed.
Sometimes we played with more than seven players, putting more than one person on the same team, giving them a diplomatic manpower advantage.
The drama and tension in person just can't quite be replaced. Although the anticipation of a move when you're playing correspondence is absolutely exquisite. Burning someone in a 3 month old game is its own wonderful experience.
Where would someone find a committed group to play with?
I am curious if in person games have as much backstabbing in them as play by email sessions, as I always tend to get screwed over and over again by shady dealings of other powers.
It's 1907, no one trusts each other anymore and everyone hates everyone.
Most of the strategy revolves around predicting when, not if, your ally of convenience will backstab you, and how long you can afford to trust them before you'll need to stab first.
It's nice to see these things popping up. I've used similar web interfaces before and they're great. Diplomacy is best played with the full complement of 7 players, and 7 is an awkward number of people to get together for a game that can last up to 3 hours, but see 1-2 people eliminated in the first hour.
I mean, if you were to take two different groups and put them both through the Prisoner's Dilemma game, presenting it as "The Cooperation Game" to one and "The Betrayal Game" to the other, wouldn't you expect to see some difference in the outcomes? I'm sure someone has done this before; perhaps someone with better google-fu can dig it up.
"up to 3 hours", though? 6 hours is the fastest I've played (limited experience, but still...)
And don't worry too much about being hated. Having people obviously out for you makes for easy recruiting of their enemies.
In a recent game  I played Turkey with two neighbors who conspired against me. 2vs1 is quite a certain death sentence and I was tempted to give up and just let them take me. Then I resisted that and started talking to everybody. Instead of defeat for me the game ended in a draw.
We didn't consider the impact it would have on new or potential players but it doesn't seem to have scared many newbies away; in fact we get regular feedback that our site was easier for new folks to get into. Personally, I think knowing that backstabbing is a core part of the game going in helps soften the blow when it first happens.
Also, gunboat style (no communication possible) is quite popular online.
In our case, we really do encourage people to go buy a copy of the board game, preferably from your local nerd shop. There's a lot to recommend playing Diplomacy online (I believe it was the second game playable by mail published after chess), but there is something special about playing in person and having all the physical materials.
I made a website for a fork of UNO years ago called "Hot Death UNO" and was sent a cease and desist from Mattel for it. I changed the name and the look of the cards and poof, no more problem.
So you can say at 3pm you wnat to be in a game. It can start at 3 am, and by the time you realize you are in a game you have already lost. With seven people, probably many in different time zones, I haven't yet seen a turn of my game where at least two people didn't move.
Cool site though.
I love the sandboxing feature on backstabbr, but I so so wish it was faster. I would pay good money for a native Windows or iPad client that loaded the current game state and was strictly a fast sandboxing tool. Sandboxing is so heavily "what if" where you want to explore maybe a dozen paths quickly that the tool becomes frustrating when it can't keep up with your ideas.
Or some other way to sign in that does not require Google?
Our group started on playdiplomacy a few months back, but migrated to backstabbr for our games shortly after. PD's good too, but responsiveness, clean visuals, easy sandboxes, and strong mobile support were huge draws for backstabbr.
I think we originally tried PD just because after a 20 second review of each site, it looked like you had to have a GM on backstabbr (not true at all, adjudication is easily fully automated, we realized after a longer look). Also, the google login requirement kept one friend from joining our game, but most of us saw the google login as neutral to a perk.
I've been really impressed with the site, really hope it takes off and you all find some way to get handsomely compensated.
It is the classic map with a twist: it starts with a build phase, so you can choose between armies and fleets.
vDip also has a click-on-the-map interface, although I prefer the drop-down variant.