Its not potentially penetrated...it is.
A few weeks ago i was talking with a AIVD (Dutch intelligence officer) advisor at one of our industrial clients who got hacked by a foreign source.
And during a coffee break the Tor network came up in a conversation, and the man said: Tor is 100% secure from a user perspective (User vs User) but for a law enforcement agency its a open book, yet while the network itself is pretty secure and offers a challenge to intercept, the relay and hive nodes are a open book. So tapping into the nodes is much more beneficial to tapping the network then to try to intercept a connection.
The general consensus is that even the Tor network travels over main Internet backbones, and while being encrypted with 2 way encryption the Thor node and hive structure does process the raw packets and by doing so it opens a number of ways to directly read the data and to tap into the protocols used.
So from a user POV the Tor network is really save and it is, but it does provide only a very minor boost to privacy.