The blogosphere is abuzz with reports that Google has once again tweaked its ranking algorithms. If I correctly understand what's going on, this could be an ugly one for many data publishers.
Apparently, in an attempt to raise the quality of search results, Google is now on the lookout for web pages that appear to be database-generated, contain few inbound links, are several levels below the home page, and offer limited amounts of information. Sounds like most of the online directories I run across. The bad news is that once identified, these pages will now be pushed way down in its search results.
The sense of those who watch SEO very closely is that Google is going after e-commerce sites with low-information product pages. Data publishers could just be collateral damage.
Time to panic? Not yet. Google is not offering up many specifics, and even the SEO alchemists aren't sure what's going on yet. The most important thing for right now is to know that something may be going on, and watch your traffic and test your search result ranking in Google to see if you are being impacted. There's lots being written on this, but here's a good place to start if you want more information.