The Chinese refer to Tiananmen Square Massacre as 6489 (June 4, 1989).
I was just reading a Chinese blogger and was initially confused by the occurence of strings such as June 1234, 3149683659.
I wonder if the numeric identifier was chosen because of the ease with which it can be embedded in innocent strings and thereby fool the filters.
The blogger also makes use of a variety of obfuscated versions of 'democracy', 'political', 'censored' etc. Can't help but think though that filters could be tuned to watch for 'Ti@@@@@@@en Square'.