I guess Google isn't too happy about that decision, because if you search for [yahoo search] in Google, Google ranks AllTheWeb.com above Yahoo Search!
I tried this on several browsers, logged in and logged out, with personalized search on and off and AllTheWeb.com in all cases outranks Yahoo Search for a search for [yahoo search]. Here is a picture:
The same search in Bing or Yahoo do not return AllTheWeb in the top results.
So why is Google ranking AllTheWeb for Yahoo Search? Well, because Yahoo decided to use a "temporary" redirect, a 302 redirect - as opposed to using an "permanent" redirect, a 301 redirect, from alltheweb.com to search.yahoo.com.
Forum discussion at Search Engine Roundtable Forums.