It all depends on application. If you're an OEM that has a customer that requires their computers to have ultimate long-term reliability (like in the medical field), then this is one less moving vital part. The overwhelming majority of DIY applications are for gaming or other high-performance applications. This doesn't really lend itself to that. Maybe you should watch the video from Greg Salazar and then ask yourself "How many DIY builders are really going to be interested in a fanless solution that limits what their CPU will be capable of?" because I can't think of any. People who only engage in light use of their PCs tend to be the ignorant masses who tend to buy craptops or "brand-in-a-box" desktops.
The only DIY application that I could see this being useful for is the HTPC but most people throw those together from spare parts that they no longer use. In those cases, sure, this might be useful but if I know Noctua, this will not be cheap and the sound of an HTPC can be mitigated simply by putting next to, or behind the TV, a good distance from where your sofa is.