I have a very difficult time convincing many clients that you can't just add random email addresses to your newsletter list, etc. Most people just don't take it seriously. But spam is not only annoying - but illegal. Case in point - Papa John's.
I know a small business owner is probably never going to be gone after in the same way - but a fact is a fact. Spamming anyone, via text, email, etc. is bad business, bad manners, and against the law. Don't do it.