A week after version 2.5 of Google's tweaks to the search rank algorithm - A.K.A. Panda - rolled out across the Web, new data from Searchmetrics show that the changes appear to be rolling back. Panda is designed to reduce the impact of content farms and other low-quality sites that game Google's page ranking algorithm.

Out of the 30 domains that were hit hardest by last week's changes, 10 of them have recovered to receive more traffic than before Panda 2.5, with another 10 restored to 80-90% of their pre-Panda 2.5 visibility. Only four sites did not recover their SEO visibility: bettermedicine.com, faqs.org, ohinternet.com and The Next Web.

"Previous updates seemed to be high-confidence decisions," says Searchmetrics founder Marcus Tober. "Google generally would not alter the Panda classifications for a couple of weeks. Panda 2.5 seems to be an exception to that rule."

Weekly SEO visibility for the four sites that recovered the most:

Searchmetrics measures the SEO visibility of sites around the Web. The results that they publish are adjusted to eliminate outliers in either relative or absolute terms.

For example, if a huge site like Myspace loses significant SEO visibility in absolute terms, it will top the absolute list of winners and losers for a given Panda update, even though the proportion of Myspace's page rank is not significant. Likewise, tiny sites might see 1,000% changes in page rank, but it wouldn't mean much in terms of the absolute impact of the update.

Of the 30 losing sites highlighted by Searchmetrics when Panda 2.5 rolled out, only four sites were denied recovery in the rollback: bettermedicine.com (0%), faqs.org (-3%), ohinternet.com (-3%), and The Next Web (-13%).

SEO visibility for the four sites that did not recover:

What do you think of the sites on this list? Do Google's adjustments accurately reflect the quality of these sites?