Google have a heck of a lot more data to go on. It's not just the title of Facebook.com, it's the millions of links to it that contain the word 'Facebook'.
The app store doesn't have that data, so has to rely more on titles to try and how you a specific app if you do a specific search. If I search for 'Facebook' there's a high chance I want the official app, so it should come up high no matter if it's not the highest ranked.
Of course, it's plainly open for abuse. I wonder if they do, or could, take usage stats into account as well as ratings. If everyone is using the official Facebook app despite the fact it's crap, the user is probably trying to find it when they search for it, but it no one is using My Crappy Picassa App then it shouldn't be ranked very highly, even on a search for 'Picassa'. But then you have the bootstrapping problem of new apps being hard to find, even with exact searches. Perhaps some sort of inverse relationship between age and active users would work.
Well actually, they should have more data. The description and reviews should be available to them without an issue. More importantly, they could mine backlinks for more context.
The app store doesn't have that data, so has to rely more on titles to try and how you a specific app if you do a specific search. If I search for 'Facebook' there's a high chance I want the official app, so it should come up high no matter if it's not the highest ranked.
Of course, it's plainly open for abuse. I wonder if they do, or could, take usage stats into account as well as ratings. If everyone is using the official Facebook app despite the fact it's crap, the user is probably trying to find it when they search for it, but it no one is using My Crappy Picassa App then it shouldn't be ranked very highly, even on a search for 'Picassa'. But then you have the bootstrapping problem of new apps being hard to find, even with exact searches. Perhaps some sort of inverse relationship between age and active users would work.