Comment by idle_zealot

You start conservatively, and set up a watchdog to investigate loopholes and punish those abusing them. Fund an astroturfing campaign? Congrats, that's 10 years and a hefty fine to fund the continued operation of the watchdog. You can make promotional material and publish it, but it has to be clearly labeled and opt-in, not bundled with access to something else. The problem isn't small-time promotion that's difficult or impossible to crack down on, it's that we've built a whole attention economy. So long as we make it a bad value proposition for big players we'll have succeeded.