My take on Y killing arbitrage is two fold :
1. Arbitrage
YSM/Ov they have been so keen to cash in over past few years (and they have) they have allowed thousands of partners to pawn Overture listings - which has presented massive staffing and technical issues thanks to the 'complexity' of implementing feeds and xml etc etc. They also cannot monitor the ROI on those feeds effectively as they do not have the staff to.
So....with increased fraud, big spending individuals/companies and agencies in particular (who manage most of the biggest PPC spenders - read finance and shopping) have started to complain about rogue 'partners' with huge fraud clickthroughs with their client money for little or no ROI therefore they HAVE threatened to pull completely whole accounts from Y in order to concentrate on the simpler and easier to manage Adsense (plus they then benefit from G's 80%+ dominance of UK search market)
Culling partners (as opposed to sub syndication deals) has actually been taking place since Y's implementation of a Quality Score back in mid Nov - Ask feeds and many other high volume feeds are obviously the more high profile accounts that Y is using for positive PR and column inches.
The mad thing is, from what I have heard, there has been little or NO real help to sort the problems out. ie problematical verticals or particular sources and IP's that can be isolated as fraudulent..... they have worked to try and get the quality scores up - but with few resources and manpower and now the buyout looming... long term views are out the window for short term quick fixes to maintain the big spending agencies first and foremost.
2. Quality Scores
Using Quality Score I believe is first and foremost a PR tool that they are using to try and encourage advertisers back to the new and improved YSM.
Reading that article, I don't actually agree with the author's take on what will happen to the sites that were using Ask sub-syndicated feeds :
[sic]The partners/websites will be [/sic] coming back from all those who have no other option but Yahoo
Many people will not go back to Y from Ask/Parking etc. Adsense is simpler to implement, simpler to manage, has greater Advertiser breadth and has contextual ads that work. For the parked domains - there are other options too including i believe a G version.
That's before you even factor in the fantastic depth and capabilities of the reporting system. There are also some very nice G developments coming that I know of - that I think will truly seal another nail in Y's coffin - at least in the UK anyway.
=============
So my 2p worth - Y have fu**** up their arbitrage with smaller partners big time - thanks partly to their "quality score" implementation and lack of support for partners to increase quality.
With regards to the big Arbitrage Partners and sub-syndicates - who knows - maybe they are counting 100% on a rebound effect from Ask etc.... I just can't see it happening in the way the want it to.
In the UK, from people I have met and spoken to that run/ran arbitrage, thanks to G's removal of many arbitrage accounts in mid to late 2007 and Y's own culling, they must have lost £10m+ turnover per month (if not a lot more) and of that you are talking £5m+ rev to Y UK.
Which is all great for the advertiser as it's clean traffic

- there's just not much of it.