There's  an absurd fee (non-consensus) check already. Maybe that check can be improved, but probably the wallet layer is more appropriate for this.

On Mar 3, 2016 16:23, "Henning Kopp via bitcoin-dev" <bitcoin-dev@lists.linuxfoundation.org> wrote:
Hi,
I think there is no need to do a hardfork for this. Rather it should
be implemented as a safety-mechanism in the client. Perhaps a warning
can pop up, if one of your conditions A) or B) is met.

All the best
Henning Kopp


On Thu, Mar 03, 2016 at 05:02:11AM -0800, Alice Wonder via bitcoin-dev wrote:
> I think the next hard fork should require a safety rule for TX fees.
>
> https://blockchain.info/tx/6fe69404e6c12b25b60fcd56cc6dc9fb169b24608943def6dbe1eb0a9388ed08
>
> 15 BTC TX fee for < 7 BTC of outputs.
>
> Probably either a typo or client bug.
>
> My guess is the user was using a client that does not adjust TX fee, and
> needed to manually set it in order to get the TX in the block sooner, and
> meant 15 mBTC or something.
>
> I suggest that either :
>
> A) TX fee may not be larger than sum of outputs
> B) TX fee per byte may not be larger than 4X largest fee per byte in
> previous block
>
> Either of those would have prevented this TX from going into a block.
>
> Many people I know are scared of bitcoin, that they will make a TX and make
> a mistake they can't undo.
>
> Adding protections may help give confidence and there is precedence to doing
> things to prevent typo blunders - a public address has a four byte checksum
> to reduce the odds of a typo.
>
> This kind of mistake is rare, so a fix could be included in the coming HF
> for the possible July 2017 block increase.
>
> Thank you for your time.
>
> Alice Wonder
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--
Henning Kopp
Institute of Distributed Systems
Ulm University, Germany

Office: O27 - 3402
Phone: +49 731 50-24138
Web: http://www.uni-ulm.de/in/vs/~kopp
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