I suppose my example (Fiji) should more appropriately fit under the label of "primitive agrarian communism" - it was/is not the industrial means of production that is owned collectively but the land itself. In a sense, there was no "proletariat" - and although there was a "noble" class, land-ownership was common and no-one (of the same clan) was to be denied a fair share - their certainly was no bourgeoisie to be got rid of. There is now of course, but unfortunately that has evolved in such a way that it is inextricably linked to ethnicity - unsurprisingly because, for the most part being unable to 'own' land of their own, people of non-native descent had only their own industry with which to raise themselves from poverty - and some were so successful that they ended up owning the "capital" that drives the economic progress and prosperity of the nation. But they still can't own the land. The native Fijian, on the other hand, owns the land (in common) but has very little of the capital. Odd - and almost universally perceived as 'unfair' one way or the other.
In the Mondragon case, it is the "capital" that is worker owned, but (as Noam Chomsky noted) the corporation is fully embedded in a(n otherwise) capitalist system - so in reality, whilst ensuring (as it seems to do) a more equitable share of the proceeds of the worker's labour than most other corporations, it remains entirely at the mercy of the "free" market rather the needs of the workers (let alone the people generally) - IOW it still exploits as much as it emancipates its employees.
I think both of these examples illustrate the difficulty with communism (not that I don't agree with the ideal) - but unless it is (somehow) imposed universally, it eventually just gets subsumed into the capitalist über-system (I think I just made up a German word but you know what I mean) and even a country that imposes it on itself, in terms of the "world economy", just becomes a giant worker's cooperative - and, being on national scale, probably not that efficiently run at that - which wouldn't really matter in economic terms if everyone were doing it but they're not.