It's fair to say that VANs were responsible for bringing EDI to current volume levels of transactions. It is also fair to say that interconnects between VANs were the path to their success. Traditional VANs and their interconnects built the market, now they are the market for newer technology (VAN2).
Integration is always a hot topic for the supply chain. It's a powerful tool to improve profitability by reducing costs. Like a lot of ideas, though, its effectiveness depends quite a bit on context. What works best for a small manufacturer may be considerably different than what does the trick for a large retailer. The pressure for profits may be the similar but there’s a huge difference in scale.