The authorities don't need to run exit nodes, they just pwn enough routers, have enough interception devices or buy enough netflow data that they can trace data flowing through the Tor work back to its original location.

Sure, but if that becomes a problem for you depends on

1. whether or not your request stays within the tor network or not (if you use the .onion address, no need for an exit node)

2. given both entry and exit nodes can be literally all over the world: your threat opposition level. I doubt the NSA will be happy to help French authorities trying to catch a teenager who blockaded a government parking garage).