Your experience is dated. In Guangdong Province, 2010, I found facebook & youtube completely blocked.
I also found anything containing prohibited keywords appeared to be blocked by means of sending an RST packet after a packet or two of data, so briefly you would see the text of http://en.wikipedia.org/wiki/Dalai_Lama for example, before Firefox would advise that the 'connection was reset whilst the page was loading'. Furtheremore, additional requests to that website's IP were completely denied for some random time (typically a few minutes).
Even pages discussing the filter were blocked in much the same way.
All digital cellular phone standards in use today (GSM, UMTS, CDMA, etc) encrypt SMS messages and voice calls and it is almost always enabled.
That being said the strength of the various algorithms remains questionable (shameless plug).
But to say it is outright plaintext and broadcast is plain wrong.
"Been through Hell? Whaddya bring back for me?" -- A. Brilliant