I feel like this would be pointless as the vast majority of users would
likely download the blockchain from a node that was not enforcing a tip
requirement as it would seem like unnecessary cost as in protocol​s such as
BitTorrent there is no such tips in sharing files and the blockchain
distribution is in eccense the same thing. However perhaps I am
underestimating the generosity of node operators but I feel that adding a
cost to the blockchain (assuming that all users add a tip requirement)
would lead to centralisation.

On Wed, 3 May 2017, 22:21 Erik Aronesty via bitcoin-dev, <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> IDEA:
>
> - Full nodes advertise a bitcoin address.   Users that need to download
> the block chain from that node can be encouraged to send a tip to the peers
> that served them (by % served).   Recommended tip of 10mbit should be fine.
>
> - A full nodes can *require* a tip to download the blockchain.  If they
> do, users that don't specify a tip cannot use them.
>
> CONS:
>
> For some people, this may represent a barrier to hosting their own full
> node.   After all, if you have to pay $15 just to get a copy of the
> blockchain, that just adds to the already expensive prospect of hosting a
> full node.
>
> PROS:
>
> As long as you manage to stay online, you should get your money back and
> more.   This is the an incentive for quality, long term hosting.
>
> In the long term, this should cause stable nodes to stick around longer.
> It also discourages "installation spam" attacks on the network.
>
> Fees for other node operations can be considered if this is successful.
>
>
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>