We generate a lot of natural links for BetUS.com (PR7) and we obviously try to build links (we do that very well). I get the emails every WEEK about the success and the tracking of the link backs.
From this site alone I can see that we add X amounts of links per month (less than say 3-500 links) and we check back on them periodically whether we’re still getting the link back, the state of the link (straight link, no affiliate codes, written in HTML not JS) and we notice that Google does not update the link back for a lonnnnnnnnng time.
I understand you can disagree, but when you say “Google update backlinks with toolbar PageRank as often as they can” -> this does not say anything about the update frequency, the fact seems to be that backlinks are not updated regularly. If you can show me evidence (from Google for example I would be very pleased!).
Google has been having a lot of issues lately with their Data Centers. I think this is why they are slowing down the updating of the backlink counts and information but for most quality sites it’s on a month per month basis… however, what defines a “quality site”?