Anonymous's strategy for "defeating" the FBI etc. is to publicly humiliate them and expose them to be harmful and largely worthless[1] - that goal is better served by showing off the FBI's incompetence than by guarding their own rear ends.

[1] That's not to be interpreted as a claim on my part that they are. This sentence, however, may freely be interpreted as such.

(Firefox's spellcheck isn't working for me atm (nightly, so no surprise) - please accept my apologies for any embarrassing typos above.)