[gojomo]

Probably. Unless you're working in concert with major mining power, it's still hard to engineer a successful double-spend. And by pushing their preferred observed transaction to major pools, Square could help ensure a double-spend can't succeed, or get a near-instant indication that a competing transaction exists. (I don't know if they're doing this.)

It also looks like most 'Square Market' purchases take more than an hour to deliver/ship... so the payment validity will be known before a hypothetical fraudster benefits.

[theswan]

Makes me wonder - would we ever get to a point where it's in Square/Stripe/Coinbase/et. al's interests to contribute mining power to help their own transactions along? Or is that pretty much taken care of by transaction fees?

[gojomo]

I suspect they'd just strike deals with existing mining specialists, if and when necessary, perhaps even via out-of-band (non-Bitcoin-transaction) exchanges of considerations.

[wmf]

There could be a problem with fees from a merchant's perspective because they are chosen by the sender and it's possible that someone could (accidentally or intentionally) pay with a transaction that never confirms. Merchant providers like BitPay/Coinbase/Stripe/Square might benefit from a way to pay fees on behalf of a transaction to ensure it gets confirmed.

[bradleysmith]

>And by pushing their preferred observed transaction to major pools, Square could help ensure a double-spend can't succeed, or get a near-instant indication that a competing transaction exists.

What would this even look like? is anyone doing 'specialized mining' like this, where particular hashing nodes are being used for preferential transactions?