{Curse of Echoes} is on my opponent's side of the field, I manage to put one on my side of the field. He casts a spell and I try to {Counterspell} it. Question is, can he copy the Counterspell to counter it and then I copy his copy to counter his counter that is countering my counter?
Wow that was confusing to type. Lol.
Correct me if I'm wrong, but it believe you cannot, because he doesn't cast the copy, it is just created and put on the stack. Your counter would be countered.
Also, you mean that his is on your side and yours is on his side, right? Or did you curse yourselves?
Yes, mine is on his side and vice vs.
But id like other opinions and answers, just trying to make sure.
the above is correct. since the copies arent cast, they wont trigger curse of echoes again for an infinite loop.
Will a flashback trigger the curse(s)?
Sure. You're still casting an instant or sorcery spell. The Curse doesn't care where you're casting it from.
Here's the ruling
1/22/2011 All the copies are created on the stack, so none of them are cast. Abilities that trigger when a player casts a spell won't trigger. The copies will then resolve as normal, after players get a chance to cast spells and activate abilities.