Does Google use an anti-dominance strategy in SERPs?

[Whitey]

Just recently I've been observing some new behaviour in the SERP's on highly competitive terms. The top 3 or 4 sites , regardless of link activity regularily swap positions.

For some time I've noticed sites that start to dominate a large range of positions , get dumped. Not one site that hit top position in the SERP's with even large corporate backing in the sectors i watch holds top positions [ and that's scarey for Corporations relying on the SERP's ].

Those that hold the top positions are often poor quality sites, preferred due to their inability to move beyond small levels of scale in the SERP's.

Is Google actively applying an anti domination filter in certain sectors ?

And therefore does Google influence it's commercial preference for who get's shown and who doesn't?

Any thoughts?

[idolw]

interesting, I noticed some sites that used to be strong in my area were moved back for some of their keywords to page 2-3 in the last few weeks.
However, I thought the reason was banning all the pay-per-post blogs they bought posts on ;)

[RedCardinal]

Connected to the shuffling effect in any way I wonder?

Definitely seems like there have been big changes in the way a subset of SERPs are constructed since around May.