I wrote an earlier entry describing the Verizon-specific default settings that I noticed upon getting an my iPhone 4S on Verizon.
I just found a Knowledge Base article at Apple that describes things that are controlled by the carrier settings, such as:
Carrier settings include updates to Access Point Names (APNs), MMS settings, features such as tethering, and default apps such as Stocks, Maps, and Weather.
It does mention the Stocks app, as I had noticed, but doesn’t mention Safari (though their list begins with “such as”, so it’s not complete).
Not only does a new phone come with these configurations, but the carriers can occasionally provide over the air updates to these carrier settings files, allowing them to make changes in the future.