We review our previous work in which we have shown that imaging by an ideal optical interferometric array, which suffers only from the Poisson noise of photoelectron counting, is essentially insensitive to how light beams are split and recombined. Any physically large, monolithic array such as those planned for space will however also suffer from mechanical noise in its structure. We show that inclusion of this technical noise amounts to an effective decorrelation that degrades sensitivity. We calculate this decorrelation factor for an otherwise ideal nC2 array and make some pertinent comments about its effect on other sorts of arrays as well. Finally, we review our work on ground-based arrays which suffer sharp reductions in the sensitivity compared to ideal arrays, particularly at low count rates.