While Google may have been one of the best possible tools for searching one’s own site, it was always a piece of technology waiting to be monetized and thus has commercial interests. It makes sense they would be doing this, since they are probably not going to be extracting money out of your site through DFP (Doubleclick for Publishers). If they are possibly moving more towards content and publisher placement as a way of collecting more money through their ad network, that really sucks — especially since their impartiality is what made them great to begin with.
On the other hand, there are now plenty of resources out there for someone to build an open source tool which does a bit of learning to make semantic maps about words and allow one to do a semantic search on one’s blog. Now that hardware for accelerating things like neural networks is getting cheaper and is already available in certain cloud infrastructure, it would be possible to have a fairly cheap service running an index of your site or a community of sites to perform an above average search.
If I get the time I might start working on this as a project. However, I’m just going to leave this here in case anyone else wants to start on it. I think the possible complication is needing to file a patent for the final open source system in order to protect it from patent trolls.