I wonder if this to help train users to use RealNames instead of URL's.
They tried to make people understand in the past to just type in a name into the browser, but many just didn't get it.
Maybe this is a step back to that. So let's say that the Joe User forgets to type in the search engine name before he puts in the search term. RealNames kicks in and takes him to the site most likely matching that term (for example for a brand name).
Joe User then finds out that all he has to do is type in the brand name to get to different sites.
Another reason RealNames could be doing this is to find out what people search on. This allows them, in the future, to sell keywords at a premium. (for smart tags, maybe? OK, that's a stretch, even for me..)