multiple formation detachments?

Maybe I'm missing something, so I figured I'd ask, are there any rules about taking the same formation more than once in a single army? I.E. taking two dark artisan formations in a 1500 pt. list...

No problem with that whatsoever. Nothing in the rules prevents multiples of a detachment or formation.

Nope! Hell, take it three times! Tournaments may have house rules, however, so check ahead.

Only restriction is if the Formation inclues a unique character. Those are restricted army-wide.

That's what I was thinking, I just wanted to get confirmation from my fellow dark eldar...

So, we played a 4 player, 2 on 2 style game, my DE with my buddies eldar, against AM and Space Wolves. The two Dark Artisan did their job nicely, dropping in on a 2+ from the Eldar Autarch, heat lances destroying 1 basilisk, and 1 hydra on drop. Next turn they crushed the other basilisk and hydra in cc. The two grot boats tied up both wolf guard squads for most of the game, and my buddy got the rest of the work done with his eldar, it was a complete slaughter.