Slicing, dicing, reviewing?

I like to peruse the Chronicle of Higher Education fora. You'll find a vibrant, clever, helpful, and often volatile community there, comprising academics at all stages and venues. Today I thought I'd post a topic of interest to new investigators - what's your duty as a manuscript reviewer? The particular issue at hand is how to handle what you suspect to be an LPU, or "Least Publishable Unit", the smallest portion of a study that could conceivably stand alone as a publication, but the discussion that follows is more generally applicable. As both a reviewer and a reviewee, it's good to know the different ways people judge the work of others.