Can we estimate correct size of human interactome?

A recent study published in Nature methods estimates that the human interactome contains approximately ~130,000 binary interactions, most of which remain to be mapped, and the fraction of interactions identified so far represents approximately 8% of the full interactome. Figure repoted by Venkatesan et al. are four fold less than previously reported study in journal PNAS which estimated the number of interactions in humans to be ~650,000. An estimate of the human interactome can establish the magnitude of work required to map protein-protein interactions. Similar kind of estimates have been used during Human Genome Project, although after sequencing it was revealed that the number of genes is much lower than had been expected or estimated. This ambiguity about size of human interactome is due  to unresolved  differentiation between sets of protein pairs that can interact (biophysical interactions) and do interact (biological interactions). With 22,500 protein-coding genes, nearly 250 million protein pairs need to be tested to map whole human interactome, which is only possible with appllication of high-throughput approaches. Study also revelas that high-throughput yeast two-hybrid (HT-Y2H) interactions for human proteins are more precise than literature-curated interactions supported by a single publication, which  is very much according to observation made by Cusick et al.  Although previously it was suggested that biological complexity of organisms can not be explained merely by the number of genes but may be by the number of physiologically relevant interactions, it may be interesting to note that nematode Caenorhabditis elegans appears to have a similar number of genes as humans, and now the size of interactome appears of same order. So the big question is why we are so different from Caenorhabditis elegans?