It seems that wireless network hotspots are all the rage. You can't go into a Starbuck's Coffee or a Borders Books without seeing people on their laptops and PDA's hammering away at their keyboards sending the latest chain-letter email on to all of their friends.

You can go to sites such as Wi-Fi Free Spot or Wi-Fi Hotspot List and find sites based on location and / or provider.

So- here is my question. For those who may have experience with one of these hotspots or even just a working knowledge of their security- can you tell me what you see as the security concerns when joining a public wireless network such as a TMobile or Boingo hotspot? Between TMobile, Boingo, Wayport and Verizon are you aware of anything that makes one inherently more or less secure than the rest?