I have a more off-topic (from Android/iOS) question, why did you decide to go with SMS/MMS, I understand that in theory it meant not having to build an infrastructure, and re-invent the wheel... but for me, as a customer the huge appeal is that other messaging apps free me from SMS and make use of my much cheaper data-plan. SMS is so limited and expensive compared to the amount of data I can send over 3G/Wifi, in fact, frequently sending messages on my phone is now free, but with one tied to SMS/MMS it would always cost me money to use.

Maybe it's hindsight being 20/20, but it just seems like a really strange direction to go in, so is there something other than the infrastructure and theoretical ease of use that drove your decision?