Well, I just chased two off by keeping their trade locked by spamming the mouse-click on the trade button.
Just go over to them, face up towards the sky so the cursor isn't pointing at the ground, and click that trade button like there's no tomorrow.
What's cool is that if they're in trade with someone else, clicking that trade button makes you run to where they are. If you're in trade with them and they're running away, just hit the space bar and you'll go over to them.
One scammer I chased back and forth between two districts in ToA until he either left or blocked me (hasn't been scamming either district in ToA at the moment).
Of course, you DO have to be bored for this to really be effective
No effort needed, just clicking a mouse button.
The guy was spamming that he was buying ecto's @ 8.5k and I kept whispering that I'd leave him alone if he bought my ecto @ 9k. He didn't take the bait unfortunately
Fun fun!