For example, the Kindle app (on iOS) keeps bugging me about random things that are basically ads for Kindle. The Etsy app does the same. I recently installed the AliExpress app, and it started sending me notifications daily about deals ("Still looking for wigs? Look what we found, just for you!" -- just because I was entertaining myself the other day by browsing through all the crazy crap that AliExpress sells, it now thinks I want a wig).
Apple (and Google, presumably) really should penalize app creators for abusing notifications.