They really get their information quickly.
i only have an isdn-connection, but when I checked which files where asked for (or which my prog sent information about to others) via the information phex provides, I saw, that most of them where, even those, which I would have never deemed possible, that they could be asked for so often.

So browsing isn't necessary and if you just check the queries you can get most popular files quickly without ever sending a query to the network, which the RIAA could also do.