This has been most probably discussed before. Please point me out to any official statements on the topic, I couldn't find a coherent explanation in my limited time digging around.

If I understand correctly, Iota defends against sybil attacks through having the clients attach PoW to transactions. Yet the PoW is by its nature computationally expensive, thus energy-draining and time-consuming. It looks to be a less-than-ideal fit for embedded devices, where the energy availability/consumption and the computational power are scarce, sometimes critical resources.

Moreover, I assume that a GPU or an ASIC (comparable in scale with the current top-level bitcoin mining chips) would exceed the total PoW capability of tens of thousands of embedded devices (or maybe more). So thinking about this disparity in resource availability (PoW capability) between different classes of devices, isn't it paving the road towards cost-effective sybil attacks?

How does Iota address these challenges?