Bitcoin's block chain size is currently around 300GB and increasing. How much of an issue is this in the future? If internet speeds and storage capacity increases at the same pace as Bitcoin's blockchain size, then this is a probably not a big deal but what if the increase in the blockchain size outpaces it? What are the implications? Would less people be able to run nodes/mining and therefore threaten decentralisation? Are there any other threats that need to be considered?