I think that is a very narrow definition of the value of a search engine.
I would say that a search engine's value is in helping me find what I'm looking for.
Often - as you point out - what I'm looking for is new information.
But there are plenty of other times, when I know exactly what I'm looking for, but I either forgot where it is, or it is simply faster to search for it than to go digging through folders, apps, etc to get to it.
In the case of Matt's story, maybe he remembered that someone posted a picture of him playing werewolf, but he couldn't remember who posted it or where they posted it to. In this case searching for it was very useful and gave him exactly the information he was searching for.
Or maybe I know that I have a picture from some event last year with a friend, but I can't remember - or I'm too lazy :-) - to dig through my folders to find it. Being able to search for it is awesome.
It's analogous to the way search works on my phone, or on Windows 7 or mac spotlight.
If I want to find a contact on my phone, I can dig through the contacts app, or I can just type the name into the search box.
If I want to find a program or a document on my computer, it's often faster to just search for it rather than navigate through menus and/or folders.
This new search feature is simply bringing that same kind of functionality to the data you have in the cloud.