The chief executive of Backpage.com pleaded guilty to state and federal charges including conspiracy and money laundering, and agreed to testify in ongoing prosecutions against others at the website that authorities have dubbed a lucrative nationwide "online brothel," authorities said. "For far too long, Backpage.com existed as the dominant marketplace for illicit commercial sex, a place where sex traffickers frequently advertised children and adults alike," U.S. Attorney General Jeff Sessions said in a statement. "But this illegality stops right now." Backpage brought in a half-billion dollars since it began in 2004, mostly though prominent risque advertising for escorts and massages,...