It's not just RUDE and UNETHICAL to send bulk spam SMS messages to random people, it's illegal. Visit this link: http://esupport.fcc.gov/complaints.htm ,fill out and return the electronic form. Make sure these guys get hit with a BIG FINE from the FCC.
Thanks for the link, D K!! I filed a complaint with the FCC as well after receiving a spam text message from these guys. I also encourage anyone else who gets this spam text message to do the same. It took about two minutes.
Probably sequential dialing. Automated sequential dialing is illegal in some areas but a text message is not technically dialing. Florida law makes it illegal to send electronic mail with false identification and the definition of electronic mail does include messages between telecommunications devices. But if the sender did not provide false identification and did not include a virus or other damaging contents, then that does not apply. I am not a lawyer, so if there are any lawyers who think there is a way to file a criminal complaint against these folks, tell us how.