As of a couple of years ago, to the best of my knowledge, cell phones in the U.S. were not using the SIM chip technology that is common in Taiwan. Cell phone users could not simply pop out a personal SIM and stick it in another phone and continue as usual, with the same phone number and all personal data, etc.
Has that changed?
If so, any details would be appreciated.
Those would be the 2 big players that rock SIMs. Don’t know if anyone else does.
AT&T has had SIM phones available in the US at least since 2000, and I believe several years before that.
If I’m not mistaken AT&T is Cingular (someone bought somebody or changed a name or somethin’ 
.)
Even if so, it still wasn’t the standard. I’m trying to determine if that has changed and if SIM phones are the norm in the U.S. now.
Ran across this website:
cellularabroad.com/q_as.html#gsm
A summary of the FAQ is that GSM (SIM card compatible) phone coverage in the U.S. is only offered by a few companies and then the coverage is not complete (as vast as non-GSM coverage). Additionally, U.S. GSM phones operate on different frequencies than nearly all other GSM phones from other countries. Why, when the U.S. finally got in gear on GSM, did it decide on different frequencies than everyone else, and thus end up still operating a non-standard system? Odd.
All said, it sounds like there would be very little practical compatibility between U.S. and non-U.S. GSM phones/networks.
One loose end is the whole tri-band, quad-band issue (what is it, how does it effect this topic, etc?).
Almost all “cool” phones are tri-band these days. I forget the numbers (something like 1900, 1800 and 900.)
I’m not sure what you mean by “standard.” Every country will have a different answer for that. If you do have a tri-band phone, you can take out your Taiwan SIM, buy one from Cellular or T-Mobile, put it in your tri-band phone, and you’re in business.
I was in the US over Chinese New Year and did this with my 3G phone (which must be quad band or something.)
I don’t think you’ll have any problem finding a GSM carrier in the US using SIM cards. Cingular is damn near everywhere, especially now that they merged with AT&T. You can always go to cingular’s site and check their coverage.
Also, I have a chinese friend who always buys asian model phones that he uses in the U.S. Every time I see him he has a different phone, and he’s never had any problems. He even helped me buy a phone when he was in Taipei. Like you, I was paranoid about making sure it was triband and all that but like miltownkid said, pretty much all the cool phones are triband.