you can't do that. when you implement search you need a global view over the collection to understand what are the most relevant documents. You are describing the paradise of the spammers :)
Would make SEO much easier, and I guess would increase the amount of spam on Google. Any website can return the search results that it would like.
I guess search engines could apply a score to each site so that those who spam, get down-graded, but then how would they do the scoring? By crawling? Then you still need a crawler and might as well build your own index.
Perhaps commercial products can improve over the quality of results, but simple text and keyword search can work this way.