Anecdotally I've seen two primary reasons posed for not running a node:

1) For enthusiasts who want to altruistically run a node at home, it's
usually a bandwidth / quality of service problem. There are tools to help
work around this, but most users aren't sysadmins and would prefer a simple
configuration option in bitcoind and a slider / selector in the QT client
to throttle the total bandwidth usage. This issue has been open for years:
https://github.com/bitcoin/bitcoin/issues/273 - if you want to make it
easier for enthusiasts to run nodes, I'd start there.

2) For businesses, it's not so much an issue with the resources of
installing / running / maintaining a node, it's an issue with the lack of
indexing options offered by bitcoind. Thus the business will also need to
run their own indexing solution - an out-of-the-box solution such as
Insight or Toshi might work, but for more custom indexing you have to roll
your own software - this is where it actually becomes expensive.

Depending upon the query volume / latency needs of the business, it may not
make sense to bother administering bitcoind instances, the indexing
software, and its databases - using a third party API will probably be more
efficient.

- Jameson

On Fri, Aug 7, 2015 at 1:50 PM, Gavin Andresen via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

>
> On Fri, Aug 7, 2015 at 12:30 PM, Pieter Wuille via bitcoin-dev <
> bitcoin-dev@lists.linuxfoundation.org> wrote:
>
>> If the incentives for running a node don't weight up against the
>> cost/difficulty using a full node yourself for a majority of people in the
>> ecosystem, I would argue that there is a problem. As Bitcoin's fundamental
>> improvement over other systems is the lack of need for trust, I believe
>> that with increased adoption should also come an increased (in absolute
>> terms) incentive for people to use a full node. I'm seeing the opposite
>> trend, and that is worrying IMHO.
>
>
> Are you saying that unless the majority of people in the ecosystem decide
> to trust nothing but the genesis block hash (decide to run a full node)
> there is a problem?
>
> If so, then we do have a fundamental difference of opinion, but I've
> misunderstood how you think about trust/centralization/convenience
> tradeoffs in the past.
>
> I believe people in the Bitcoin ecosystem will choose different tradeoffs,
> and I believe that is OK-- people should be free to make those tradeoffs.
>
> And given that the majority of people in the ecosystem were deciding that
> using a centralized service or an SPV-level-security wallet was better even
> two or three years ago when blocks were tiny (I'd have to go back and dig
> up number-of-full-nodes and number-of-active-wallets at the big web-wallet
> providers, but I bet there were an order of magnitude more people using
> centralized services than running full nodes even back then), I firmly
> believe that block size has very little to do with the decision to run a
> full node or not.
>
>
> --
> --
> Gavin Andresen
>
>
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>