Let me talk about some backgrounds first. In taiwan, most people use yahoo.com.tw. As a result, SEO works are mainly done for yahoo. I was studying the ranking of sites for a certain keyword in yahoo (Chinese keyword, of course). I found that for one particular keyword, the website at the first position in yahoo has more than 50k of backlink. Than I try to study the backlink structure from yahoo site explorer and find that nearly all the links are blogspot spam comments. I was shocked that that more than 2/3 of the sites in the first 8 pages in yahoo for that keyword are spamiing in the same blogs.... It seems that all these sites are run by the same person. (they must be making a lot of money ) I assume that yahoo will not count nofollow links but this study somehow imply that yahoo make count nofollow links..... Of course it may only work for taiwan yahoo only....
Just discuss with my friends and they find that all 2/3 sites mentioned are only one landing page, they are directing the visitors to the same main site.... so it is very clear that it is spam ....
The nofollow tag is associated with Google not other search engines. They may be getting a lot of Yahoo search traffic, but when Google catches on they will get banned. I know what search traffic I would prefer.
you assume wrong. It's a google thing. It means 'dont pass pagerank down that link', nothing more. It certainly DOESN'T mean 'dont follow' despite the name.
sure, then it means that this kind of blogspot spam comment will work perfect in taiwan as long as they do not change the alogrithm, since it is yahoo.com.tw that dominates taiwan
Unfortunately different engines have different algorithms... and as an SEO you have to go with what works for the engine where your targetted audience most often searches. In the US, 70% of the search traffic is Google, so I concentrate on Google. I NEVER even consider how I rank at Yahoo!, MSN, Ask... though I do track rankings there. But any traffic I get from non-Google engines is just extra bonus to me. Yahoo! and the other engines have MUCH less sophisticated ranking algorithms and are MUCH more likely to be manipulated through techniques like those you describe. Google, however, utilizes a lot more anti-spam filters in their ranking algorithms which leads to MUCH better search results... Not much you can do about it. Just figure out your target audience and where they search, then plan your SEO around how that engine ranks URLs.