A monopoly is not that easy to get on the web, unless you can somehow contrive to control the ISP, homepage, browser, web protocols, or user system to lock other providers out. Yahoo doesn't have control over ANY of those. If they don't give what people want, people will try another site.
I'd like to see more competition, of course: at this point the ODP is too much the "only directory game in town" for my comfort, and Google is too much the "only search engine". But the amount of investment it would take to seriously challenge the quality of either of those is daunting. Yahoo may provide a "second source" with inktomi and its own directory (both of which are comparable to the ODP and Google), and then there is the MSN-zone, which is all about wondering how they can get golden eggs and pate de fois gras from the same customers. But their attitude is too deeply ingrained "quality search results are the ones that bring most money back to us" to ever compete for serious websurfers. They'll do fine because of their enormous lockin efforts and capabilities, but that's all.
