Originally Posted by Braindrain

The firewall does nothing other than protect your computer from intrusion. For public networks, people can install "sniffers" and snatch your information if it isn't encrypted. A VPN does exactly that - encrypt the traffic so they don't know what it is.

Is it absolutely necessary? No, as long as you don't log in to anything while on a public network. If you check gmail, banks, etc - yes, I'd say it's necessary. Will your ID get compromised the 1st time you don't use VPN? Probably not, but you'll be kicking yourself if it does.

I'm absolutely paranoid on public wifi networks. For a wired network at a hotel, it's a little better but I still make a point of taking precautions.