It's not simply a political factor (although it mostly is.) This has nothing to do with the Fed (which I believe should be done away with.) The powers the USG use to go after groups that potentially threaten it existed before 1913 (even though more powers have been added since then.) The Fed has nothing to do what so ever with this discussion.
I misunderstood your comment then (my apologies for down voting it then.) My best guess is that there are probably a number of reasons why the Feds are targeting specific groups.
It could be as simple as the Occupy movement represents a target rich environment.
Edited for some grammar & clarity.