SMS is extremely popular among those with service providers using
GSM. Of course, in
Europe, that's everybody. In the
U.S. and
Canada, though,
GSM is probably in third place in the digital popularity contest, behind
CDMA (commonly referred to as
PCS) and
TDMA.
The SMS protocol has been ported to CDMA, allowing CDMA phones to receive messages, but the first version of the port did not allow the phones themselves to send messages. Thus, the only way to send CDMA users "text messages," as most providers refer to them, was through a web page. To add to the difficulty, CDMA SMS messages cannot be received while roaming off one's home network, unlike GSM SMS, which can be sent/received worldwide. The implication was simple -- SMS hasn't caught on nearly as well in America.
Update 4 January 2002: Perhaps CDMA SMS roaming is on the way. While in New York recently, presumably roaming on the Verizon Wireless NYC network (since nTelos stops in Winchester, VA), my nTelos phone received all my usual automated text messages (sports scores, etc.).