Before revision:  The seminal impossibility result of Myerson and Satterthwaite 1983 shows that even for bilateral trade, there is no feasible (IR, truthful and budget balanced) mechanism that has welfare as high as the optimal-yet-infeasible VCG mechanism, which attains maximal welfare but runs a deficit.
After revision:  The seminal impossibility result of Myerson and Satterthwaite 1983 shows that even for bilateral trade, there is no feasible (IR, truthful , budget balanced) mechanism that has welfare as high as the optimal-yet-infeasible VCG mechanism, which attains maximal welfare but runs a deficit.