The major impact of this decision will be on consumer adoption. Now, every time I want to make a transaction, I need to keep track of my taxes. I know that some wallet services are already developing ways to keep track of this automatically, but that's just an extra headache for the average consumer. This in essence will force consumers to think of bitcoin more as an investment, rather than a "currency" they can spend, and that will impede adoption.
I know nobody here likes to hear it, and I feel like a lot here in SV are tuning this out, but bitcoin is really, really struggling to find a relevant use case with consumers. Regular consumers have absolutely no reason to use bitcoin. The "1-click" payment and 1% price discount are not appealing enough to the average Joe who already gets 1-2% cash back, airline miles, and consumer protection on his credit card (and 1-click checkouts on many e-commerce platforms). And more regulation isn't helping the "crypto-anarchist" decentralization angle either. Add price volatility to that and it kills the consumer use case.
But... micro-payments? Consumers have always hated them. http://www.openp2p.com/pub/a/p2p/2000/12/19/micropayments.ht... (Shirky, 2000)
But... international transactions? Hard to beat the fees at https://transferwise.com.
Bitcoin is great, FOR MERCHANTS. But consumer adoption is going to determine whether or not it succeeds on a grander scale. Unfortunately, Bitcoin does not solve a problem for consumers. Especially with tap-tap mobile payments around the corner.
When it comes to money, consumers want to be insured and cuddled and protected and not run the risk (however small) of being criminally liable for transactions and have someone to speak with if they make an erroneous transaction or have their card stolen. And they can already do all that, which makes it tremendously difficult to compel them to change the habits they've had for in forever to adopt a system that does not provide them with significant advantages.
I've been in bitcoin since 2011 and used to be a big believer, but I don't see bitcoin gaining traction with consumers, in part because of the huge regulatory risk. Any significant threat to the banks' business will be met with harmful regulatory control (friendly reminder: Wall Street banks fund the largest political lobbies in Washington). It could be destined to eternally remain an investment instrument (like gold) or find very targeted applications (like machine-to-machine payments). The underlying blockchain technology could be of more use (if adopted by the banking system, for example) but that is still far in the future.