it can be one of the two reasons: 1) you stopped promote your directory. 2) i think that after panda and penguin people are concerning more from where they get their links.
This could be a slow season. As a guess, most of the people will be off from the internet to watch the coming Olympics.
In the OP's case, I am pretty sure it has more to do with the fact that what he's selling is not necessarily on the up and up...
May be it is because people now know where to submit and where to not ...and bdw owners of standard and quality directories are still getting pretty much submission that they even feed the g.penguin and g.panda with there left overs
It has very little to do with popularity and more to do with the fact that the PR he pushes here is always FAKE. Notice how he never responds when I call him out! Want proof, there's a nifty search by user feature offered in VB! Beware!
Sorry to see people using bad techniques when trying to market their directory. I think this is a big part of the reason why directories are having so much trouble these days. In order to regain the popularity and power they enjoyed before, directory owners have to start doing things the legit way or else most directories will only be seen as repositories for spam.