The health-website bubble, inflated by purchased search-engine traffic, is deflating. As rumored for weeks, Waterfront Media, an operator of health websites, is buying Revolution Health in a $300 million deal. Waterfront's network reaches 14.7 million visitors a month; Revolution, 11.3 million. WebMD, the largest operator of health websites has 17.3 million. Yet the combination won't displace WebMD, one industry insider says: "This really is 2 + 2 = 3." Where the deal does add up: Case, as a Waterfront board member, will be free to take credit for whatever success Waterfront realizes.