There are three things at work here: 1. How stale the index/data is. 2. The coverage of the data. 3. The processing algorithms that do magic on the data to retu

There are three things at work here: 1. How stale the index/data is. 2. The coverage of the data. 3. The processing algorithms that do magic on the data to return results. These are the key things every search engine deals with. Google, Yahoo!, and MS Live compensate for stale data by scheduling their crawlers very cleverly. Google has published a few blog posts a while back about how it does it (I'm sure it's even more improved now). The breakthrough of W|A is number (3) in my list above. They kick ass and frankly make search much more useful than anything we have now. You're no longer searching for pages that have the info, but getting answers directly. A Cambridge, UK, startup called True Knowledge does this too, and it's impressive (W|A is much better in data presenation though). So for an alpha product, please do not judge it by have stale or incomplete data. It simply can't have all the data fresh from the get-go. Judge though by how good or bad are the algos that power the search. The data is relatively easy to get hold of when compared to writing awesome analysis code.