dusky - 12:19 am on May 9, 2010 (gmt 0)

FWIW, we have an established PR7 site and haven't seen any change in long-tail traffic (or any other traffic that Google sends us) in the last several months.

Every dog has its day, or shall I say, don't speak too soon, G* is moving data in batches / chunks, most large sites are going to see some change, be it for the best or the worst, they will see a change, just hope is for the best I guess. Don't take this as a scaring statement!

Because many large sites are seeing a change, that will have a snowball effect, and repercussions will be got as a domino effect on almost all sites on the Internet in G*'s index, mainly due to the power of backlinks G* attaches as a major ranking factor in its algo. Maybe your sites is spared but if other important sites that link to you see a negative / positive change, so will you!

One of my sites was PR8, now it's PR5, that's because few large sites had natural backlinks to it, some removed them (old news), and some sites themselves were demoted...
When I mention PR I mean the traffic volume that is interesting, when it was PR8, it had millions of unique monthly users, now PR5 and is less than a million monthly uniques.