Now that this thread has reached 40 pages it has become pretty impossible to read through all the posts. But, clearly there is something going on with the iPhone and the sim card for more than just a couple people. After reading a fair number of posts, I get the feeling that this sim problem might be generated by a whole list of causes...software?, hardware?, bad sim cards?, bad sim card placement in its slot?, a dirty sim card slot?, etc. Different things seem to work for different people and some people have had no luck getting anything to work.
We own 3 iPhone 4s' in our family. My wife and I have had no sim card problems since getting the phones over a month ago. But, last week my daughter received the feared "Sim Failure" notification on her iphone 4S. Along with that, there was "No Service." We are on the Verizon network. Since the "fix" some have had success with (at least temporarily) has been to shut off the iPhone (not sleep...OFF) and then turn it back on I tried that. Boom, her phone had a restored connection to the Verizon network and her iPhone has been fine for a week since then.
We are pretty diligent in our house about regularly Shutting Down our MacBook Pros and not just putting them to sleep. Maybe about 3 times a week. We have been told often that this is "Best Practice" by the tech department where my wife and I teach. We USED to do the same with our pre-iPhone 4S cell phones for the same reason. But, since getting our iPhone 4S' we have not completely shut them down nearly as often as we are doing the "plug in at night iCloud backup thing." Nevertheless, I have shut my phone down regularly enough. I have done the same for my wife's iPhone. But, it crossed my mind that I have let my daughter be in charge of her iPhone. Since I told her to plug in her phone at night to initiate the auto backup I was curious about when she had last shut down her phone. She said..."Never." So, for over a month my daughter's phone was never shut down.
It could be a total fluke that her phone had the "Sim Failure" and she had never shut down her phone, but it could also be that one of the several ways to generate a "Sim Failure" on the iPhone 4S is to never shut it down in order to allow it to "clear out the bad and bring in the good." When I called Apple Care about this, they recommended I go back to shutting down the iPhone about 3 times a week as we had done with previous cell phones and see what happens. They in no way implied that this was the universal fix for the sim problem. But, they did say that in my case it may be the reason for my daughter's "Sim Failure" as it is fairly common for phones that are never shut down to eventually develop a whole range of functionality problems.
Sorry, this has been very long winded. But, I didn't want to post something and advertise it as more than it is. The fact is, a segment of the population that are experiencing "Sim Failures" may be having the problem because they are not shutting off their phones on a somewhat regular basis. Maybe once a week is enough. Maybe more. I have no idea. I'm going with 2-3 for now and see if my daughter's phone becomes "Sim Failure" free. As I said, my daughter's iPhone 4S has been "Sim Failure Free" for a week now. I will repost if her phone fails again despite more conscientious shutting down of the phone.