For those who'd like to read it, here's an article from Bloomberg that provides excellent context for Jamie Dimon's remarks. My take? Bubble or not, Bitcoin is not going away and neither are cryptocurrencies, in general, going the way of the hula hoop. It serves a need.

And here's the video of Elevations' NcNamee, declaring Bitcoin to be in a bubble.
https://www.bloomberg.com/news/videos/2017-09-01/roger-mcnamee-says-bitcoin-is-probably-in-a-bubble-video
Enjoy!