My mobile carrier data plan allows only connections using HTTP(S) proxy or IMAP, SMTP, POP3. I can use every protocol encapsulated in SSL/TLS with HTTP(S) proxy (CONNECT method). No destination ports ...
So here's your Average Joe at a coffee store, using the open Wifi on his shiny new Android phone. Obviously there are the same issues with using a laptop or any other device on an open network, ...