Do you use this commercially? <- no. just as test. "and have tools to detect and prevent such abuse" <- This was my assumption too. I tested all large carrier

Do you use this commercially? <- no. just as test. "and have tools to detect and prevent such abuse" <- This was my assumption too. I tested all large carriers. Verizon, however doesn't seem to have these limits in place. With a verizon sim I can push out about 200 texts per hour per device. If you get rejected in my tests depends on the receiving carrier. "it's that carriers essentially have a cartel and can set prices however they want" <- yes. Carrier to carrier is where things are interesting. Sprint gets quickly blocked by ATT for example. But, wow, a UNLIMITED TEXT plan is pretty cheap...