Through the popularity of Facebook, crystal radio enthusiasts from around the world participate in groups such as the Crystal Radio DX Contest group, Crystal Set Radio Group (two groups with the same name), Home Built Radios group, and Radio Experimental Mundial (South America) . Over 8,000 individuals spanning the globe routinely contribute to these groups demonstrating that interest in crystal radio building and listening is still alive and well. Fascinating blog post here on the history and construction crystal radio sets which still appears to be a thriving hobby.