Lightboxes for this are terrible. Please don't do it.

I'm sure lightboxes drive up shares per view, but I wonder if there's data on how they impact views in the long-term.

This is cynical, and arguably (probably) a net negative, but in nearly all cases, intrusive stuff like lightboxes, modals, and exit intent stuff works. It increases time on site, conversions, whatever metric you want to measure.

This is the part I don't understand

> It increases time on site,

My interpretation is that they increases time-on-site by pushing away people that aren't committed enough to wade through bloatware... and I don't understand how that works in the long-run.

Is it more profitable to push away customers so you get high-quality data on the core customers, and increasingly targeted advertising? How does that work out in the long-run when you need to replace lost customers?

More shares per view translate to more views, period. While sites certainly need to balance user experience with their need to grow, aggressively asking for shares works, and sites that do it will always do better traffic-wise than those that don't. I realize that ultra-white hat developers don't like this fact, and many would like to see it cause some sort of detrimental effect on the sites that do it. But unless the implementation is egregiously bad, most users simply don't care.

I've learned to intentionally stop all videos before they finish so that you don't get another unrelated video auto-started, you don't get some weird ad or other overlay that makes scrubbing back in the video impossible, and so you don't have to see a bunch of "subscribe to my other thing and here's a video preview of it that makes no sense without sound!"