High risk Wifi networks
With the amount of commercial WISP's out there, it really is scary what you are able to "see" in the air. Modern software makes it very easy to see e-mail login details, websites visited, cookies with password details of websites like facebook, etc, etc. It is really amazing and it is a legal time bomb waiting to happen in my opinion. Even encrypted (which is not that many) networks can be hacked.
Here in my area there are relative big WISP's running totally unsecure networks with 300 - 1000 clients. Companies like lawyers, wineries, doctors etc, all their sensitive e-mail communication at risk.