Online platforms with prime advertising space like Facebook and Google do not allow drug, or drug-related promotions on their sites, leaving a large share of marijuana advertising to blogs and podcasts, newsletters and print media. And while experts say Facebook and Google — which control the lion's share of digital advertising in the country — are unlikely to change their policies until pot is legalized at the federal level, and television and radio come with their own sets of rules, industry members are left to navigate a complex web of state-by-state regulations.