[morganvachon]

>Blackmail: pay us or we will cut your advertising revenue.

As others have said, not blackmail, but extortion. Blackmail would be the threat of revealing embarrassing or financially harming information.

>Tortious interference: Your company counts on (double_digit)% ad revenue. We're going to harm you in significant ways... unless you pay.

Another name for that here in the US is racketeering, or running a protection racket. It's the classic "pay us X dollars or we'll destroy your store/break your kneecaps/kill your family" only with a digital/financial threat.