I think something that anyone who isn't validating should be aware of is
that cgminer(which powers the vast majority of the current mining network)
doesn't allow for a pool to revert to mining on the previous block due to
the way chain tracking is implemented.

https://github.com/ckolivas/cgminer/blob/master/cgminer.c#L4727

On Fri, Dec 4, 2015 at 4:43 PM, Rusty Russell via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> Gavin Andresen via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org>
> writes:
> > Overall, good idea.
> >
> > Is there a write-up somewhere describing in detail the 'accidental
> selfish
> > mining' problem that this mitigates? I think a link in the BIP to a
> fuller
> > description of the problem and how validation-skipping makes it go away
> > would be helpful.
> >
> > RE: which bit to use:  the draft versionbits BIP and BIP101 use bit 30;
> to
> > avoid confusion, I think it would be better to use bit 0.
>
> Yes, BIP9 need to be adjusted (setting bit 30 means BIP9 counts it as a
> vote against all softforks).  BIP101 uses bits 0,1,2 AFAICT, so perhaps
> start from the other end and use bit 29?  We can bikeshed that later
> though...
>
> > I agree with Jannes Faber, behavior with respect to SPV clients should be
> > to only tell them about fully validated headers.
>
> A delicate balance.  If we penalize these blocks too much, it's
> disincentive to set the bit.  Fortunately it's easy for SPV clients to
> decide for themselves, I think?
>
> Cheers,
> Rusty.
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