Currently I see a lot of topics talking about people "successfully double spending" but if you understand Bitcoin you should know that there is not one single case of double spending in the entire blockchain (there cannot be as that is the very problem that the Nakamoto consensus was created to solve and if it didn't solve that problem then bitcoins would be worthless and we'd have never had heard of Satoshi at all).

It is entirely possible for an unconfirmed tx to end up never confirmed and the same UTXOs to be used in a new tx that does get confirmed but that is not technically "double spending" except outside of the blockchain if a merchant accepted the unconfirmed tx (which they have been told again and again is not safe to do).

So any "double spending" is not actually happening within the blockchain itself but from outside users that are not correctly using it.

Even one confirmation isn't necessarily sufficient as one or two block re-orgs do happen fairly regularly (although most of those don't end up involving the same UTXOs involved in different txs).

Perhaps someone could come up with a better term other than "double-spend" to describe what amounts to a "race to be first confirmed" to avoid the misunderstanding that is occurring.

Whilst this may indeed be possible it is something that is not being really used at the moment and I think it will require specialised software to do this which basically means that merchants are still going to use payment processors rather than just say a Bitcoin client (personally I think that we don't want to even have payment processors in the future).

Basically I think that the 1 MB limit has actually been a good thing in showing us all the issues that Bitcoin as a payment system has (beyond the confirmation times).

Hopefully these issues will all be resolved over time and Bitcoin can become a realistic alternative to other payment systems but I don't think this is likely to happen for at least some years (but its other great use cases such as person to person transactions are functioning very well right now).

I'm not sure what you mean by "involved in the blockchain.info project" (as I've never even used it as a wallet and I certainly never did any work for them) and of course offchain txs are a reasonable solution (I have not said that they aren't).

It is people that keep on insisting that Bitcoin should be used for all txs (big and very small) that I think are just not being realistic about what Bitcoin (at least in its current form) has been built to do and do well.

Actually in the specific case of something like a cup of coffee it is the vendor who will be taking a big risk if blocks are near to full (be they 1MB or 10MB) as there are multiple threads about txs that never confirm.

How hard would it be to write a simple little wallet that purposely crafts txs that won't confirm (before they are dropped from the mempool)?

As soon as that kind of thing is reported (assuming it does occur) then you will see merchants spooked and stop offering Bitcoin as a payment option (which is also why I don't see any urgency to push for Bitcoin to be used as a general purpose payment system).

Honestly it has been exactly "cups of coffee" that many of the large block size proponents have been using as their own mantra (this particular use case certainly didn't start with me).

In any case I am referring to small payments that currently you would be far more likely to be using a credit card and for which reversibility is something that one would want without much hassle (you don't want to have to involve a lawyer to get back 10 dollars from a bad merchant).

Again for person to person transactions Bitcoin works extremely well (I have purchased Bitcoins for RMB in the past for people that had visited China a few years back).

There has been quite a bit of bad news lately in regards to Bitcoin as a payment system and frankly I'm not at all surprised (I've always thought that Satoshi really hadn't quite thought this aspect through very well).

Although the blockchain invention is perhaps the most significant thing since HTTPS for the internet, Bitcoin as a payment system really doesn't work very well (and I was trying to use it myself for this purpose over the last few years but have basically given up now).

Apart from the slow confirmation times and the low TPS issues - for any average consumer what is the benefit of making an irreversible payment?

Adding to that the complexity of merchants having to deal with txs that may never confirm due to minimum fees with full blocks you simply don't see anything even vaguely threatening to the likes of VISA or Mastercard.

I've already stated that Bitcoin should be focused on the remittance market and as a potential replacement for SWIFT (as it is a very good fit for both of those) but still some people just seem to think that Bitcoin won't have "made it" until they can buy a coffee with it (and most of the people who are saying this are people who probably don't even have enough BTC to buy much more than one coffee).

Now I've thought about it more I think that those pushing for very large block sizes really are rather confused as to what they think this will achieve. If you can't reverse your payment (due to say not getting something delivered) then why would any online purchaser prefer to use Bitcoin (and talking about escrows is just silly as people don't use escrows when normally purchasing things with credit cards as they don't need to - you can generally just complain to your credit card provider and the merchant will lose out which is what most consumers prefer).

What Bitcoin can do *now* is act as a store of value (and is about the most superior such thing apart from the volatility which in recent months seems to be a lot less which is appealing to those wishing to use it for this purpose) so I think that it is far more important for the project to focus on this strength (and its potential to disrupt the remittance market) than on replacing existing payment systems (other than as a person to person payment system which is another great strength that it has).

A transaction can still be "legit" but never get confirmed - if a tx has less fees than required then it won't be propagated at all (so the merchant wouldn't see it in the first place) but if the fee is exactly the bare minimum and the size of the tx is large then it is entirely possible the tx won't get confirmed (a situation that was occurring during the so called stress testing).

If he isn't using a payment merchant then he is actually going to leave himself wide open to people paying without correct fees and this is a "double spend" attack that requires virtually no skill and does not require sending the second tx within seconds (such a tx can be sent anytime later).

Assuming only a few BTC txs are expected in a week then maybe as long as he does check how many txs have confirmed at the end of the week he can decide whether or not it is worthwhile to continue taking the risk.

Bitcoin is not ready for "purchasing coffees" would be my answer.

Unfortunately it is actually quite simple to configure software to pay no fee at all and if the UTXOs are not old and the tx is small (and perhaps made up from many micro payments like most ad-sig posters wallets would likely do) then there is a good chance such a tx would not confirm before being actually dropped from the memory pool (restoring the funds to the purchaser - there are many topics created here about txs not confirmed after 2 days, etc.).

So you don't even need to "double spend" you just spend without enough fees to ever confirm!
(note that this will especially be true at times when people are purposely spam attacking the network to try and fill up blocks)

I guess the only chance for the vendor is if their Bitcoin payment processor identifies that the tx doesn't have enough of a fee to realistically confirm.

You are probably one of only a handful of people who get paid in Bitcoin (assuming the amount you are paid is more than just a couple of coffees per month).

Expecting everyone to accept BTC as a payment option just because you are paid in BTC when the merchant might only get one such BTC payment per month (or per year) is a little hopeful IMO (although there are actually quite a lot of merchants accepting payments in BTC at the moment).

When there are tens of thousands of people being paid their wages in BTC I'd expect to see a lot more merchants providing a BTC payment option but for the most part I think a lot of merchants have only said "we accept BTC" for the sake of some publicity (rather than any significant amount of sales).

I am not a Bitcoin enemy but I think Bitcoin is losing its way in getting pushed around with this whole block size debate (that seems to be far more about politics and control rather than anything else).

Patience is the first thing I think those that actually believe in the invention should have - buying coffees for BTC might end up being the final result but it isn't what we should be caring about now.

Well - with hardly any employees now clearly they aren't expecting a lot of business are they?

(assuming that they can continue with only 10% or so of the staff shows that there can't be much business going on)

Well - I don't think your coffee purchasing is going to save BitPay is it?

They had over 30M in VC funding (from what I had read) so if the loss of 2M causes them to sack nearly everyone then what happened to the other 28M?

If "business was booming" then I very much doubt they would have needed to sack so many employees (and also it wasn't that recent - it happened last year from what I read).

Yes - they take an *obscene* amount of fees from migrant workers (often as high as 30-50% when you are talking small value transfers).

I have actually some inside knowledge of some new remittance businesses based around the technology (although unfortunately they are not keen to use Bitcoin itself - it seems that Ripple is actually making more inroads now).

As I think this really is the ideal area for Bitcoin I would be willing to offer my help to any serious business wanting to work on getting this happening.

And clearly there is no need to increase the block size to do that (am actually agreeing with you).

Huh?

If no-one is using Bitcoin to pay for things then how on earth are these business benefiting from larger block sizes?

I think that the BitPay announcement (reducing their staff by a large percentage) is perhaps proof that Bitcoin is not being used by large numbers of people to buy things.

It isn't surprising to me (as I've been pointing out for weeks before this happened) as pretty much no-one is being paid their salary in BTC and the hassle (and fees) to purchase BTC does not make it attractive to then want to go and spend it for usually no discount (as most people allowing BTC payments are using BitPay or the like and do not offer a cheaper selling price - it's just a different payment option).

Sure we have maybe hundreds of ad-sig posters on this forum that earn enough to pay for 1 coffee per month but a new world economy that hardly makes (I really can't see Starbucks franchises being keen to train their staff for a few coffees they might be able to sell per month for BTC).

Until people are being paid in BTC they are simply not going to be using it to buy things (apart from the "early investors" most of which have already bought whatever toys they wanted to already).

What I'd like to see the focus being on is remittance (the main reason why I actually started using Bitcoin back in 2011). Compared to other methods Bitcoin should "kick ass" in this area but unfortunately it has made virtually no impact in a market that is worth billions in profits per year.

Maybe you didn't read that BitPay has sacked most of their staff today basically because "there are hardly any customers" (at least not enough to sustain their current business model).

So we should increase the block size for businesses to serve customers that actually "don't exist"?