A major Google page rank update has punished large scale blog link farms and similar sites indulging in heavy cross linking by dramatically cutting their Google page rank scores.

There is some suggestion that the changes may be related to the sale of text link ads, but at this stage this is not backed by evidence, and a range of sites I checked that are selling text link ads were showing no change in page rank.

The only clear change appears to be among large scale blog networks and similar link farms, where each site in the network provides hundreds of outgoing links on each page of the blog to other blogs in the network, in some cases creating tens, even hundred of thousands of cross links. Previously such behavior has been rewarded by Google with high page rank, although it would now appear that this loop hole may now be shut.

Blogs in the TechCrunch network (we don’t link heavily on each page..nor do we have a particularly large network) and the Gawker Media network (who like us don’t go nuts with links) maintained their page rank whilst blogs across a range of other networks saw big decreases. The AOL owned Weblogs Inc was not immune, with leading Gadget blog Engadget dropping from PR 7 to PR5, Autoblog (6 to 4) and DownloadSquad (5 to 4).

The move by Google could well cause many smaller blog networks, including a number with funding, to close given their heavy reliance on text link ads and related sales that depend on strong Google page ranks for each site. Although traffic alone can and does sell ads on bigger sites, a drop from say PR7 to PR4 in one example makes the ad sell that much more difficult, particularly on blogs with little traffic. I’d suggest that the Deadpool will soon see a number of new entrants.

I guess that means I’ve got to watch what I link to!!