There exist Duolingo addicts. If you count that as "productive intellectual activity", then they're a great example. I'd certainly argue that it is productive.

Amazon etc have all this video surveillance and problems with making AI smart enough to gain useful data from it; I'm wondering when someone connects that to a video game like in Stephenson's "Reamde" so that pasty basement game nerds worldwide can contribute to the massive state panopticon.