There are lots of smart people out there agonising about how to make their idea viral and get it spreading out across the web. Whether they are in music, advertising, software or anything else that can spread across the web, they are thinking about this problem, and most are focusing on the proposition or the idea. Ideas are what reach a critical mass, create a dominate standard, become a web phenomena, a hit record, or a underground movie sensation. To say good ideas always trump bad ideas is generally true, but in reality its not always the best proposition that wins.
Betamax was an superior proposition to VHS but VHS still won. Dairy Milk had a superior ad campaign to Galaxy but it still lost market share (see post). The Backstreet Boys are a crap band but they still top the charts. The truth is that process is more important than proposition in a market that is made opaque by the subjective interpretation of ideas. If you get your marketing machine performing more effectively you win. That was the lesson from Betamax vs VHS.
We know from decades of studies that the diffusion of innovation is key in all of this, as shown below.
Each step in the diffusion of innovation requires its own process if it is to be successfully crossed. This means creating an experience that not only has a contagious proposition at its heart, but also has contagious processes built into it, such as: send to a friend, social bookmarking, social networks, and incentives that reward recommendation or as Seth Godin says Sneezing that infects the rest of the hive. Betamax lost because people didn't sneeze enough when they bought the product. It never developed network effects, which is a form of power you get from increasing the number of people in your network (see Metcalfe's Law).
This is why in addition to thinking about message, and medium as classically done, we now also need to think about the process, or what I'd call the modus.