One of the issues I've often had, when applying notions of corruption, is that different systems (obviously) have different ways they're supposed to work. One view of corruption uses as its basis the system's ideal, another uses the viewer's perspective. The simplest viewpoint, and perhaps the one most accurate to the meaning of the word corruption, is that only deviation from the system's ends should be considered corruption. This has certain frustrating problems when comparing corruption between two systems -- an equivalent act between a system that aims much lower and a more ambitious system may simply be "that's how it's supposed to work" in the first and a glaring problem in the second. Intuitively it seems problematic to say that a system with less ambitious goals is less corrupt, but perhaps this is because of the complicated origins of the word corrupt -- probably born in times before the wider perspective that relativism gives us was widespread, its modern most clear meaning still feels a bit awkward. In an attempt to resolve the situation, we might try splitting the term, finding a new term to apply to the degredation of the spirit and the sphere of interactions that's viewer-local rather than system-local. This is one of the issues that we see in our current political/economic system -- it does not inspire a high degree of virtue, and while it has problems with corruption by its value system, even were it not corrupt in that way it would still fall quite a ways short of what humans are capable of, properly cultivated. This poses another question -- if we had two systems, one of which aimed very high and fell short, and one of which aimed fairly low and came close to its goals, should we judge more on closeness to the goal or the absolute virtue? (The first is a corruption-centric viewpoint). Is this even a productive way to think?
I will make the possibly bold claim that this is what is missing from the traditional Marxist/Communist philosophy -- Virtue is a characteristic of civilisation, having followed and at times been ahead of the historical dialectic. Composed of a set of values and habits that both people and institutions have, it has changed in form, exchanging influences with the current form of government as humanity steps towards the more civilised. No form of government can long survive virtue in its populance that is insufficient (or inappropriately shaped) for its function, nor can virtue readily survive in a population (or class) under a system with less virtue. Attempts to bring about socialism will require just as much an official change in form of the state as a change in form of the social reality, all the way down to a personal level, or the revolution will fall astray.