Since your post was in response to me I'll quote you and try to respond. You asked about the probability of a 12-man group running two raids, both on elite, and not receiving a single raid item. Under the assumption that there is a 1/4 chance per person of receiving a piece of raid loot on elite (as written in the Mod 5 release notes), that sums to a
0.10% chance. This is also assuming that the two raids are independent of each other (there is no reason why they should be dependent). That is a very low probability, one in a thousand. Impossible? No, but highly unlikely.
Now a question you may ask is,
what if the raid looting chance doesn't scale with difficulty - ie elite really gives only a 1/6 chance per person. The probability of a 12-player group running two raids with the 1/6 "normal difficulty" loot chance, and not receiving any loot, becomes
1.26%. Now you're at one in a hundred, still very low, but more likely than 0.10%.
Which was the case here? Impossible to say, unfortunately, and I feel very bad for those that were cursed by the loot gods. But maybe the developers should re-examine the loot drop ratio to see if it really does scale, because The Ick's example is a one-in-a-thousand chance.