WiFi no Internet connectivity, switch to 3G automatically | Blackberry vs iPhone and Android

There are a lot of points where the Blackberry is still a lot better than an iPhone or an Android phone, but I'm only going to write about one of them now.

Internet connectivity

When I mean Internet connectivity, I mean how the phone automatically detects if it should use 3G or WiFi, and the three of them are good at doing that.

All of them, Blackberry, iPhone and Android phones automatically detects a WiFi zone, and then switch from 3G to WiFi and when they are out of the WiFi range they switch back to 3G (or EDGE).

This works great when everything is working as you it has to, but what happens when there are problems in the middle? Which of them is "intelligent" enough to detect such issues and act properly?

Here is our scenario.

We have a WiFi zone, where our phones have been connected in the past, so they "know" how to use it, as soon, as you come into the range, they will connect to the WiFi zone and start using it for everything. Suddenly the DNS server stop working, or the Internet (say ADSL) behind the WiFi router lose connection to the backbone. Now you still have WiFi connection (the wireless router is on, and the DHCP is working), but there is now Internet. With a computer you could do

ping www.google.com

And will get no answer. Can you guess what is going to happen with our phones?

The iPhone and Android will still be trying to use WiFi, and will not realize there is no connection, you will stop receiving emails, twitter updated or anything else. You might think everybody just forgot about you, unless you try to browse the web, and realize there is no Internet, and then manually disable the WiFi, you will be connected but disconnected from the Internet.

The Blackberry on the other hand, will immediately detect that it has lost connection and while still connected to the WiFi zone (still trying to use it as soon as it becomes available again), it will switch to 3G or EDGE, and you will still have a smartphone the other two were not that smart :)

Hope this could be improved in the future, if you know how to solve this issue both in the iPhone or Android, please let me know.