Some iPhone 4S owners are reporting problems with their new handsets where the 'No SIM card installed' is being displayed. This is not a new problem.
Here's typically how the problem manifests itself:
Got the new 32GB iPhone 4S today from AT&T, activated the phone was working all morning, I started experimenting with Siri and a couple minutes later the phone was hotter than usual and I get Sim Card failure, and Bad SIM messages. The phone now only says No Sim. I get home take out the SIM card and put it in my previous iPhone 4 and it works just fine. I then put in a blank micro SIM into the new iPhone 4S, but it still says NO SIM. Thinking the SIM reader got fried some how already.
Annoying, but this isn't an iPhone 4S specific issue - it also affected the iPhone 4, and apparently it's down to a design flaw (or perhaps manufacturing imperfections) with the SIM card tray eject mechanism causing a short circuit with the SIM card contacts.
The folks over on the Woo Blog came up with a nifty fix for this problem back in 2010 - all you need is a little tape. I know that this simple fix has worked for quite a few people. Otherwise, take the problem up with Apple.