As we move away from performance based metrics and towards engagement based metrics in display advertising, it's interesting to see interruption become a trend again. Historically, ad products that prevented readers/users from doing what they intended to do on your page were frowned upon (if not outright condemned).

(TheCut.com Interstitial)

Yet, despite this concern, the "Interstitial" (and all its various incarnations) has only become more pervasive. It's safe to say this is the result of its immense value as a branding vehicle: the audience is already highly engaged and a slight interruption provides a perfect opportunity to make an impact.

(Forbes.com Welcome Mat)

That said, I'm not sure where the "Welcome Mat" really fits in this landscape. Sure, there's an engaged audience, but only because they're forced to be. Beyond choosing to visit a specific url, their attention hasn't really been captured at this point. It's effectively an interstitial that sits between the reader's intent and the content.

(BusinessInsider.com Welcome Mat)

Feels to me like we can do a lot better.