[nitwit005]

I suspect this is comparably easy to measure since it's often a single event? I know some YouTube sponsors do so because they see the traffic/sale spike, which lets them estimate the effect.

You may recall some books spiking up the best seller lists because Oprah recommended them.

[giarc]

In the case discussed here (celebrities pumping ICOs) it would be easy to manage because they likely have affiliate links or specific urls. Even without those, the ICO could watch incoming traffic over a certain time and see the spike of IG visitors after a post.

In my original comment, I was more referring to advertisement like Tide putting up a billboard. How do they know it works? Well, I'm sure they do market surveys "Have you seen this billboard?" but it's probably full of bias. But in the grand scheme of things, it's just for market awareness as I said. Keep Tide on the minds of consumers.