From Xenzie:  According to the rules he is correct in all accounts. Any time a creature is flat-footed or flanked the rogue gets his sneak attack bonuses. This applies whether or not the creature is facing him or not (it's a sneak attack not a back-stab). Only creature's that are never flat-footed can't be sneak attacked, unless they are flanked, unless they are immune to flanking also. This also means that you can sneak attack every attack if you have more than one if you meet the requirements for a sneak attack, not just the first attack or first round. This makes Rogue's sneak attack very useful and very deadly. However some DMs may not like the power of the ability and limit it to sneak attack rounds, talk with the GM about it. Xen

I would once again like to state that a rogue sneak attack is not a BACKSTAB. It's a quick attack that makes it through defense and armor to hit a vital area of the body, thus causing more damage than a normal strike. A sneak attack could be anything from a kidney punch, a groin shot, to a poke in the eye. It's hitting a vital spot not stabing someone in the back. So facing and whether or not the person knows you are there is not the point. Xen

From Array50:  I have always treated sneak attacks in a simple way, the reason it is a sneak attack is that the monster/villains/polotention/ect. DOESN'T know the rouge is there. Once the rouge has made it, the victim knows he is there, doesn't matter if he tuns around (Which I would never do myself.) Take the described moment , a monster with 2 rouges facing him, one on each side, most of the time, he would turn sideways so he could SEE it coming again, so one attack is all they would get for back-stab, in my mind, any thief's solution to a fight should be "Hide in shadows, move silent, back-stab and tumble out of the way if the thing lives.." I have had thieves successful fight dragons using this methodology, in lower levels, battles don't normally last more than a round or two in my groups, if they are going to win, they know it before the second round, if not, they get out of the area and cover there backs. Of course so far they haven't really been challenged (Its a new group, I'm just warming up to them hehehehe) Just my opinion.

From Scottenkainen:   The concept of "sneak attacks" needing complete surprise is a holdover from previous editions, as the "back-stab" ability of thieves. The former should work well in any powergamer's campaign, and the latter should work well anywhere else.

From Sean Gernant:  "the reason it is a sneak attack is that the monster/villain/polotention/ect., DOESN'T know the rouge is there"

I disagree. The reason it is a sneak attack is that the rogue has taken the time to learn how to choose his target carefully, and since he's attacking a comparatively undefended flank, he has the opportunity to choose his target. Instead of fighting face to face where he has to look for an opening in his opponents defenses, dipping his dagger in where his enemies shield/parrying weapon isn't, he is attacking his opponents undefended areas. He can decide to slip under the armor and through the ribs to puncture a lung, or tap a kidney, or slice a hamstring. a successful sneak attack is a combination of knowledge, opportunity and intent. Rogues are slick, sneaky, smart and nasty. This is reflected in the sneak attack.

Mark Allen-West: The Player's Handbook states on pg 47:

"Sneak Attack: If a rogue can catch an opponent when he is unable to defend himself effectively from her attack, she can strike a vital spot for extra damage. Basically, any time the rogue's target would be denied his Dexterity (whether he actually has a dexterity bonus or not), or when the rogue flands the target, the rogue's attack deals extra damage"

THEREFORE: a rogue's sneak attack in 3E is VERY different from the backstab in 2E. A sneak attack is an attack that takes advantage of the rogue's opportunistic fighting style. A rogue can sneak attack anytime he/she flanks an opponent or the opponent loses DEX. With this in mind, in the first part of the question; Yes, rogues may sneak attack every round provided the correct conditions exist. As for the second question, yes, both rogues would gain sneak attacks every round. But even a monster/creature of dismal intelligence wouldn't stand in the middle for very long.

I've found that playing this way does not "munckinize" nor "powergame", it is a balance. First of all, consider how many creatures are IMMUNE to sneak attacks. There are quite a few. Secondly, it creates opportunities for both the GM and the players to use strategy in combat instead of the usual "I run in and whack it with an axe `til it dies"

 

Jim Kelleher:   I agree kinda both are true. If the opponent knows of the Rouge's presence then he/she will try to see that the Rouge has not an opportunity to attack an undefended side. So in part that is where the sneakiness comes in. Otherwise the rest is certainly true and I make them SNEAK! if they run into combat their opponent will see them coming and take defensive stances so both are true. :)

 

Esper Ranger: Sounds like this 2 rogue technique has story potential for the Knights of the Dinner Table. Perhaps Stevil and Weird Pete of the Black Hands can use it.

From Thrandorian:   This is one of many instances where the rules and logic may part company. There is a certain logic to the idea that an engaged opponent is unable to protect his/her back. One could further suggest that knowing the second thief is there and doing anything about it are two different things. Thus the defenders awareness of the second thief is a non-issue unless you feel that surprise in itself makes you more easily hit.

It is also necessary to balance what appears as real-life logic to the need for game balance. Your scenario Jeremy, subsumes that the opponent will turn one way and then the other. This might be true sometimes, with low inelegance opponents but rarely would I think so otherwise.

Also all action is supposed to take place simultaneously regardless of the illusion of multi-linear time created by "initiative". If all actions during a round take place simultaneously, then one Thief/Rogue would have to wait till the following turn to attack anyway and that would negate the advantage of two Thieves/Rogues.