There are certainly people who are paranoid of public wifi networks, but for most of us the local Starbucks provides an adequate wifi connection to safely update Facebook without fear of being hacked...
Public wifi networks are only going to increase in density.
To not connect to a public wifi network because you don't know everyone else who might be connected is just paranoia.
I applaud companies like Delta who are spending large amounts of money to bring accessible technology to large numbers of people.
Hacking wifi connections at public hotspots is an extremely rare occurrence. You are much more likely to fall for a phishing scam or have your weak password guessed than you are to be hacked in this way.
How many of you use the same username and password for all your Internet forums and shopping websites. Do these places store your info unencrypted in their database? Do they offer you a retrieval option for your password? If so, you have already given your username and password to people you don't know... Poor password management is the leading cause of hacked accounts.