Difficult to say what has changed without a time frame...but as for future developments, perhaps have a look in to LSI (Latent Semantic Indexing)
Briefly - If you search in Google right now for "apple" you will get the Mac website and a whole host of websites about the fruit. Obviously when searching for the word apple you may be interested in computers and related topics, but the current algorithm will not take the semantic relationship into account and just look for websites that contain the word apple; LSI will.
Change your search from "apple" to "~apple" for an example of how the results may look taking into account LSI. Obviously as I say this is one for the future and the above is a very very basic example.
Feel free to add a time line for "what's changed" :)
