Currently, Crucible uses table based rendering, which could potentially blow out the DOM with large reviews (i.e., greater than 1000~ lines of diffs).
The solution is to progressively render each line of diff, so that there isn't so many dom elements. This has been implemented in Fisheye's side-by-side view, and should be used in crucible.
The problem may be in how we might have to render comments associated with the diff. Not sure how that can be solved yet.