Texting scares the hell out of me, for legal reasons alone, but it can still be very effective. Kevin Frye is correct when it comes to a compliant opt-in/opt-out request. Many salespeople believe that they can send them from their personal devices, because they are not "the company", but truth is that they are held to the same statutes as any corporation.
For that reason, if you are going to send text messages to a prospect, it MUST be done through your CRM service provided they are using the legal opt-in/opt-out requests. If you send a text through the software and it is declined, all texting ends right there. However, even though it is being sent through a tool, it NEEDS to be written personally. The one absolute NO-NO and something I urge you to run away from is automating any text messages or SMS campaigns through a tool. Opt-in or not, if just one uninvited text slips through the cracks, you can be in serious sh-hot water.