In June 2006 I wrote an article called "Trendy Directories : Countdown Has Begun ?" in which I tried to anticipate what will happen to directories, at some point, when Google will hit them.
Quote from June 2006 article : "The axiom : Search engines will degrade and penalize some but not all directories."
This happened in December 2007 when Google implemented the fight against paid links. Many powerful directories were downgraded 2-3 points of page rank while the average page rank of directories went down by 2 page rank points.
Quote from June 2006 article : "The question : Will this happen on automated algorithmic bases or a human rating will be involved ?"
Seems like the answer is in the middle : while it looks like certain big selling links directories were hit manually (their backlinks count suggest this) it's sure that the algorithm that set the weight of directories backlinks was recoded.
And now to the current times... it's worth to submit to directories ? What's their value in the current SEO system ?
a) It's certain that directories backlinks still have a weight in passing page rank. We can tell by looking to websites that have exclusive backlinking from directories and still have a page rank.
b) "Special" backlinks a.k.a. heavy priced paid backlinks can trigger now the "Google Attention Algorithm" and the consequences for the paying website can be very heavy. See c) for a more deeper connection.
c) A special attention should be paid to directories that accepts only paid links. It's almost sure that Google tagged this directories as "selling links websites" and it's sure that the benefits aren't to great.
So the question is : were to submit and were to buy links ? The problem show up when putting "buy links" and Google banning paying links.
The answer is : buy traffic by having your links emphasized compared to the other links in that neighborhood.
This mean webmasters should focus now in submitting to directories that accept free links and , if they really want to stay on top, purchase top featured positions that give traffic and pass a better page rank than regular links on 43 page. Webmasters must pay attention to the balance between incoming and outgoing links, a too much quantity of outgoing links on a good page rank page can also trigger a "human review" and flag the website.
Conclusions :
Directories are still worth the time but worth a lot less money when it comes to buy heavy priced links (really, do you think it's worth 50$ to have a link on a 0 page rank page, page 13, deep in a directory ?). So heavy priced directories, that accept only paid links, should be avoided. They don't worth the money.
Directories that accept free links and charge only for top link positions that give traffic should be the target now and highly regarded by webmasters that want to build their SEO optimization directory submitting section. Because you don't pay for the link but for the top position that gives traffic.