This is all well and good, but (perhaps ironically), it's not addressing how the children will want to use their laptops. The Network is the Computer, and failing to address this is regressive. Our modern "First World" computers are used increasingly as clients, thin or otherwise, and the trend is for mobile phones to be thin clients for internet cloud back ends.
I fully understand the reasons for the laptop to be sufficient unto itself and I understand that Third World infrastructure presents huge obstacles. However, I hope the OLPC project is not discounting the strengths of the laptop as a thin client. If it makes it ideologically easier, think of it as a hybrid client, somewhere between a rich client and a thin one.