Many people use this "I am feeling lucky" feature and have reported upto 80-90% accuracy. I often found it be a great defense against phishing especially since you can search right from Firefox address bar. But I was in for a shock when I hit the button this time, this is the page that came up.
The site that came up was a phishing site. See the url that ends with "shyou.org." I dont know what has gotten into Google algorithm to rank a phishing site the top most for such a simple query. You can try the query here.
Both firefox 2 and IE 7 showed only website certificate errors but passed the site as not a phishing site.
Update 1: Searching for 'yahoo alerts' also gives the same phishing site as the first result.
A little google search has found some suspicious records of this site.
This site is talking about how .shyou.org is faking Googlebot, read here
Also I couldnt find any official page from shyou.org saying that they are indeed a proxy site.
The only page I could find was this, http://flouri.shyou.org/wikihome
and it was japanese site for flouri fans.
The ssl certificate they have is from CAcert.org, both Mozilla and Microsoft have so far refused to acknowledge them as valid. read here
Last but not the least this is the first time I am seeing a proxy site high up in the search ranking for such a popular site like Yahoo. But I have to agree the issue is open..