The converse is possibly even more interesting: what tech were you convinced would fail but took the world by storm?
Snapchat. But than again if we look at their finances (and stock), they have always been in the red and are resorting to selling glasses and hotdog costumes now (huge losses). So maybe they aren't that successful after all.
An app whose only novel idea is that the messages and photos you send delete themselves after some time, except for the fact that once they're in your friend's phone, they can of course take a screencap, or just have an app installed to store them... so the whole idea is based on cluelessness about basic security... and yet, there it is.