[myrmidon]

Sure, but how many "correct" decisions are not made or drag on forever because of vetos?

Allowing veto power to single participants is often crippling for institutions in practice, because you allow every political adversary (internal and external) to freely pick the weakest link whenever he wants to sabotage or paralyze decisionmaking.

This already happens in practice with the EU, and the Polish-Lithuanian Commonwealth is a textbook example of how such a mechanism essentially doomed the whole thing.