It's because people are back at work as Zak suggested. Therefore they don't have as much free time. Mailshotting won't make more posts if the people physically can't get to the web. The userbase needs to expand to push the post count back up rather than trying to get the existing users to post more (although that will obviously help)

The thing is - we have what 2000 people registered they don't know about all the new stuff and aren't all hitting the forums regularly.

think a mailer about Hot Pot would be good :)

I did submitt it to /. but they can't have liked it.

Moby-Dick
I did submitt it to /. but they can't have liked it.

it was well written too :) plenty of puns ;)