Wow.... such a nativist flavor to some of the remarks here - specially by players who learned about diplomacy from this site, and have only played on this site.
As someone who has been an evangelist FOR this site among the PBEM and FTF communities I still interact with (including the elite ACD group), I have to say that some of those of you defending this site with knee-jerk reactions need a wider perspective before you try to defend webdip with such reactionary arguments.
charles, Duke, and JECE bring up some seriously important points. if we at Webdip decide not to do anything about them, that is fine, but to simply ignore them is choosing to refuse to respond to reality. They are correct - the solo rates on this site are abnormally high - even in WTA games. the PPSC variant is a mutated variant of the original game and is NOT real Diplomacy - but some of us have argued and lost that debate long ago. The lack of a human GM DOES reduce the quality of both play and results (an explanation for kestas further below). Having the FULL press options (mulitple player press) IS one way to increase anti-solo coordination - specially when coupled with the slower than "normal" deadlines... keep in mind, in "normal" PBEM games each season takes about a week to play out.
All of that said... and though I'm in full agreement with charles and Duke and the others who have probably played PBEM for almost two decades now, I still think the improvements provided by this site outweigh its drawbacks... and that is why over the past 3 years, I've played 100 games on here, but zero PBEM games and I've enjoyed my Diplomacy experience more than ever before... even more than my Cat23 and Academy days. keep in mind that PBEM and Judges were themselves variations of the original FTF diplomacy. the Original game never called for a GM so that itself is a mutation of the original in order to serve the particular means of the new medium or platform.
to charles, Duke, & other PBEMers: a key point some others have raised is that there is a much wider 'range' to the players on this site. with over 26,000 profiles and some 3,500 (and growing) active players this site FAR outstrips the likes of diplomaticcorp for example (some 800 profiles if I'm not mistaken). Even Cat23 in its heyday did not have a 1000 people on its email lists...
I will admit that in the early going when you FIRST join this site, when you are FORCED to play low-point and low-quality games, as an experienced player it can be a HUGE turn-off. specially when you have built up both a reputation and experience on some other site. I personally came here after having played dozens of games on Cat23, diplomatic corps and then on the Facebook version of this application. On FB I had played some 16 games and had a 100% win/draw record - I was top-10 in points and playing with the best players on that site... but I still put that aside because I knew that after 3-5 months of play here, I'd have a much larger pool of great players that would provide me with even more enjoyment...
so for you and those like you who join webdip from other sites... there has to be a realization that it will take you 3-5 months... maybe around 5-8 games to get to a point of playing really quality games. meanwhile, play the low-quality low-points even PPSC games to farm points... get yourself to 500-1000

THEN start judging the level of play on this site.
so my challenge to you two in particular (Duke & Charles) is this: With a site this large and with the points and GR system already in place (no system is perfect, but these two are pretty good for the role they play) you have to 'deal with it' for a few months... take advantage of the lower level of play and just kick ass until you get the points you need.
Personally, if I'd be writing recommendations for old-school players who want to join this site - here is what I would recommend:
1) First play a 100point 12-36 hr deadline PPSC game (as long as you can meet the deadlines) - in this game, you will quickly figure out who will and wont talk, do your best, but dont expect expertise. use your superior tactical, strategic, and diplomatic skills to either solo for about 360

or at least survive for 250+ points... this should be pretty easy for ANY decent player. - and even if by some crap luck you get AH and get gang-raped by a bunch of noobs, then you get your 100

back and try again.
2) repeat this process one or two more times with your newly acquired points... and get yourself to the 500 to 1000 point range... this should take as little as 3-4 games or as many as 7-8 games for a pretty decent PBEM player.
3) NOW advertise on the forum for 101+ WTA games with 36-48 hour deadlines. anon or not is up to you. this is when you say, "I am a good player that wants good competition"... players like Ivo and MadMarx will come out of the woodwork to play with NEW good players...
But... when you get to this point, be ready to lose games... because the GOOD players on this site... ARE better than the good players you are used to playing on your current PBEM site. THAT is a promise. And there are more of us here then wherever you are coming from. We look forward to having you join our ranks!