The point of the Kin was that it was supposed to create a new service tier in between dumb phones and smart phones with expensive plans. At the time phones came with 2 year contracts that subsidized the cost of the phone. A basic plan came with $175 worth of subsidy which covered a dumb phone. If you added $30/month for unlimited data, you would get $350 off the the up front cost of a smart phone.

Microsoft's idea was that parents didn't want to pay that much for a smart phone for their teens. But a teen would get plenty of benefit from something in between which would allow them to use a non SMS messaging service and browse social media. Plus it had a keyboard.

It's still Verizon's fault. But it wasn't lack of promotion. The Kin didn't make sense without the accompanying plan.