This appears to be a Tracfone glitch as it has only affected Tracfone users, all simultaneously. You should submit this to their forums.
Text message received at 2/17/2012, 12:39 PM
Service: Tracfone, prepaid service
Phone Model: SAMSUNG slide-phone
Responded to received text with "test"; 90379 responded with "For more information about Tracfone services or product please visit tracfone.com"
"Stop" does not seem to do anything as this is not a subscription service. Any response to 90379's "null" message will result in the same reply from 90379.