peterdaly - 4:26 pm on Jun 24, 2009 (gmt 0)

Too much time has passed to edit my previous post...

[googlewebmastercentral.blogspot.com...]
Could this be caused by a large sudden influx of new links found in swf resources?

Many links in swf that didn't count for a "pagerank vote" may now pass pagerank. This adds new outgoing links to the link graph of a page, while decreasing the pagerank value passed for existing links on a page. Think of how many pages on the web use flash...at a global level...they could potentially all be having their pagerank value passed being changed in small ways.

For a very competitive phrase, links may contribute (directly or indirectly) as much as 50% to 70% of reason for a top placement. That being the case, small changes in pagerank at a global level (think billion pages) could potentially affect ranking for any site where links quantity/quality are borderline. Pagerank changes in sites 10 links away from you could be affecting your ranking as the PR flows through.

Of course, this is an educated guess at a root cause, and I have no firm data to support this theory. However, I do have a solid understanding of PageRank calculation and distribution, having written my own crawler and pagerank calculation in the past....and to me, this seems like a possible root cause.

1. Google has publically announced they "just added" new indexing support of external resource files from swf. Post date: Thursday, June 18, 2009
2. Links are potentially contained and indexed from in the newly loaded files.
3. General consensus here seems to be the behavior seems to be link related.

Please shoot holes in my theory.