Search on yahoo.com for a brand name such as cnn, macdonald and google. You can see a lists of shortcut links under the results that is very similar to google siteliks and live search deeplinks. Did you notice it? From when was it available?
I think it's semi by hand, like from a list of sites queried by name in Yahoo Search. For instance, Google gives WebmasterWorld sitelinks, Yahoo does not. Why not? One reason might be because not enough people query webmasterworld on Yahoo.
I'm just guessing, but maybe they used an internal list of sites searched on by domain. I haven't done an exhaustive search but I've seen consistent matches between Google Trends and Yahoo Sitelinks. When you search domains (without the .com) in Google Trends, if it shows searches then you will see the sitelinks in Yahoo.
WebmasterWorld doesn't show up in Google Trends and it doesn't show up in Yahoo Sitelinks. Babycenter shows up in GoOgle Trends and it also shows up in Yahoo sitelinks. So it's fairly safe to guess that Yahoo is using an internal list of domains queried in searches.
Site links are not reserved for the number one result in the serps. I've seen 5th and 6th results showing site links. they were laid out in a horizontal manner across the result that did not take up alot of space.
Blue Widgets spam description of blue widgets and global widget warming site link #1 site link #2 Site link #3
Yup, I see them now as well...copied Google EXACTLY on the site links. And, another thing I see is highlighted links (the one's I've visited) now as well. Weird thing is, I do NOT see any ads? Anyone else not seeing any ads as well in Yahoo! search?