Customer acquisition, I would think. The cost to them is very small compared to the gains they get by attracting so may people with an awesome, simple-to-use se

Customer acquisition, I would think. The cost to them is very small compared to the gains they get by attracting so may people with an awesome, simple-to-use service. Think of it as the "gateway" dyno. Tiers would just get in the way of the simplicity of their service.