Zillow CEO Spencer Rascoff has poured ice-cold water over his head and screamed. So has Trulia’s top exec, Pete Flint, and Better Homes and Gardens Real Estate’s CEO Sherry Chris. They are among the flood of individuals participating in social media’s latest charity craze, the "ice bucket challenge," where heads meet buckets of ice water to help raise money and awareness for the degenerative nerve disease ALS (amyotrophic lateral sclerosis). To complete the challenge, participants record a video of themselves or others dumping cold water over their heads, and challenge friends, family and acquaintances using Facebook, Twitter, Instagram or other social media platforms to do the same or donate $100 to The ALS Association (ALSA) within 24 hours. Although it has its cr...