Sorry, been busy for a few days, looks like my post has garnered quite a few responses. I will try to address a few points:
(1) Tor is incredibly secure, and I would be willing to guarantee that those people who were busted were busted based on "good old fashioned police work," such as tracing the payment methods or infiltrating the group. If Tor is properly configured, not even your ISP (or phone provider, if you're on a mobile network) has any way of knowing what sites you visit. All they can see (if they try hard enough) is that you are connecting to the Tor network.
(2) If you have a properly configured rooted phone with the right custom ROM on it and have installed and configured some of the "power user" types of apps, you can effectively ensure that your cell phone provider (or Google) will not know what apps you have installed or what websites you are visiting using your data connection. And what they don't know can't be subpoenaed. This isn't an Android security thread, so I won't go into great detail, but suffice it to say that it can be done if you know what you're doing and try hard enough.