[qrmn]

I wish that were true, but honestly, plaintext isn't fine for anything at all in 2015, whether authenticated, important, public or otherwise, whether the network is the internet or a LAN.

HTTP sites have had attack scripts injected into them by nation-states, used to DDoS others on a massive scale - and that capability, and the desire to use it, is unfortunately proliferating rapidly.

Unless you want to be part of that problem, you're going to have to go HTTPS on everything - cat videos included - no matter how important or unimportant you think it is. I really wouldn't be surprised if tcp/80 goes the way of tcp/23.

On a brighter note - the speed difference is negligible with modern cryptography, and as others have mentioned, TLS 1.3 is developing handshakes with less TCP round trips. It's possible that a future protocol (taking into account what's been learned by Google's QUIC experiment) may deliver faster handshakes over UDP if possible to avoid the TCP handshake overhead - there's energetic research in that area at the moment.