Yesterday, Rand Fishkin came out with a SEOmoz article on what makes a good web directory versus a bad one. Some of his points were that manipulative directories may have the following characteristics: are too broad, allows everyone access, uses manipulative link building, stuffs content to look natural, interlinks with other directories, and allows link bidding.
Cre8asite Forums members dissected this post and gave their $0.02 on Rand's take.
For example, Rand says that premium sponsorships on directories is shady practice. But some forum members do that.
it's no different to paying to advertise on the front page of a print paper, rather than page 23.
Other members agree with this sentiment.
I believe that's pretty much the only criticism they have on Rand's points. There also is a slight reaction in the blogosphere. Overall, Rand's article has a good direction, however, and I suggest you give it a read.
Forum discussion continues at Cre8asite Forums.