Nothing new, really. People have been acting like this for a while now, except social media enhances the awareness of it. Remember Cabbage Patch Kids? Or any "hot" Christmas toy, really.
Starbucks knows what they're doing when they do stuff like this. The whole "Oh golly gee, we didn't know how popular they'd be so we only made enough to give two or three to each store even though we've been making viral videos hyping them up for a month." is nonsense. They do it on purpose to create false scarcity just to get themselves in the headlines. So now when they make more, even more people rush to the store to buy one. Eventually, it will also result in a flooding of the market with a million different teddy bear tumbler knockoffs and then suddenly nobody will want one anymore. A couple of years ago it was the Stanley Valentine's cup at Target/Starbucks. Now Stanleys and Stanley knockoffs are everywhere and nobody gives a hoot.