That would be fun to see. It’s just too bad the Federation is so technoligically advanced compared to the Empire, that the Federation would blow them out of the water (so to speak). Actually it would be more fun to see the entire Empire get assimilated by the Borg.
Great thread. If there was an award for “Best Thread For a Nerd to Hang Out In”, this would win big time. That said, helluvan idea.
Janeway in Voyager’s pilot: The Caretaker would have died anyway, and the Kazon would have naturally gotten his tech. Janeway’s destrcution of it interfeared with the Delta quadrent’s natural progression.
TNG-- Episode where Wesley falls into flowers and gets the death sentence. Appariently Starfleet made contact with the Edo just so they could get some.
Okay, those are fine, I guess, but we all know the real violations, the classic violations, are with respect to pre-Warp societies. If your violation is a wussier, watered-down one, I think you should say so. 
Hm. Would First Contact count? Maybe the Borg were meant to assimilate us.
I considered First Contact, but I mean, humans interfering with humans? I don’t think that’s what the PD was intended to prevent.
What about the Temporal Prime Directive? Who’s to say that the TNG timeline is the correct one? Maybe we should all be drones or something.
Or the Mirror Universe? We really screwed them over.
Hey, Voyager’s should count since it spawned that God-awful series, The Pitts! (cuz they went back in time to 1996 and … Profit!)