In case you haven’t tried it already, Twitter’s search tool is very well implemented. It’s effective, slick, and very fast.
Being able to quickly and efficiently search through the life streams and conversations of a good proportion of the thought leaders and early adopters in the UK and US seems to me like something with a bit of potential… a stream that’s ripe for news and knowledge management apps like Techmeme, Silobreaker, and Google News. It’s a fair bet that conversation and life-streaming will be a valuable search domain just like user-uploaded video (apparently Youtube searches outnumber Yahoo’s).
Conventional (i.e. text and metadata-driven) image search is another search domain in which the big search companies seem willing to absorb losses. As I (and many others) have mentioned before, their willingness to do this stems from their desire to occupy user mindshare for the entire search concept, rather than piecemeal domains or verticals. As we can see from attempts by Google and Microsoft to include content-based image retrieval (CBIR) functionality that eagerness is not likely to be restricted to textual image search.
While my opinion may obviously be biased, I wouldn’t be that surprised to see “conversation” (Twitter, Friendfeed and life-streaming) and “product” (including price and visual similarity features) tabs integrated into the search boxes of the big three in the relatively near future.