Update conclusion with costs associated with higher throughput via rollups

validity_rollups_on_bitcoin.md

@@ -521,9 +521,9 @@ See [Appendix F](#appendix-f-mitigating-harm-from-compromised-cryptographic-proo
 
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-In this report, we described the history of validity rollups, how they work, and how they could be built on bitcoin. We described how, even in their simplest form, validity rollups can enable over 100 times more transaction throughput on bitcoin with no loss of self-custodial ownership security for validity rollup users compared to the ownership security of transacting on bitcoin L1. Given that validity rollups are "trustless" by design, and could be implemented without introducing new risks or sacrificing any of bitcoin's core values or features, we believe the simplest possible implementations of validity rollups would be a great fit for bitcoin.
+In this report, we described the history of validity rollups, how they work, and how they could be built on bitcoin. We described how, even in their simplest form, validity rollups can enable over 100 times more transaction throughput on bitcoin with no loss of self-custodial ownership security for validity rollup users compared to the ownership security of transacting on bitcoin L1. Such large throughput increases do not come for free though. Although validity rollups won't necessarily increase L1 full node verification costs, depending on the implementation details, due to the rollup's efficient use of L1 block space, rollup transactions could fill L1 bitcoin blocks to their maximum capacity more easily and more often than is the case for today's bitcoin transactions, which could result in an increase in L1 full node blockchain storage costs. All factors considered, given that validity rollups are "trustless" by design, and could be implemented without introducing new risks or sacrificing any of bitcoin's core values or features, we believe the simplest implementations of validity rollups would be a great fit for bitcoin.
 
-Optionally, the implementation of validity rollups on bitcoin could also support the verification of more powerful validity proofs. This would enable new capabilities for bitcoin users, such as support for more expressive smart contracts and stronger privacy protocols. Depending on how support for these more powerful validity proofs is implemented, these new capabilities could be enabled at little to no increase in the cost of running an L1 full node. However, these new capabilities could also come with new risks, such as enabling new kinds of AIM and MEV attacks, along with the possibility of provoking a crackdown on bitcoin by authoritarian governments who may be opposed to the strong privacy and censorship-resistant applications these protocols enable. Each of these new capabilities, and the risks that come with them, should be scrutinized on an individual basis, each with their own cost-benefit, risk-reward analysis, to determine whether or not they would be worth enabling on bitcoin, even in a validity rollup on L2. Some analysis of these issues was presented or referenced in this report, but should not be considered the last word on the subject. These are areas deserving of more research, experimentation, and observation.
+Optionally, the implementation of validity rollups on bitcoin could also support the verification of more powerful validity proofs. This would enable new capabilities for bitcoin users, such as support for more expressive smart contracts and stronger privacy protocols. Depending on how support for these more powerful validity proofs is implemented, these new capabilities could be enabled at little to no increase in the cost of running an L1 full node. However, these new capabilities could also come with new risks, such as enabling new kinds of AIM and MEV attacks, along with the possibility of provoking a crackdown on bitcoin by authoritarian governments who may be opposed to the strong privacy and censorship-resistant applications these protocols enable. Each of these new capabilities, and the risks that come with them, should be scrutinized on an individual basis, each with their own cost-benefit-risk-reward analysis, to determine whether or not they would be worth enabling on bitcoin, even in a validity rollup on L2. Some analysis of these issues was presented or referenced in this report, but should not be considered the last word on the subject. These are areas deserving of more research, experimentation, and observation.
 
 <h2> Appendix A. Comparing validity rollups to other protocols <sup id="appendix-a-comparing-validity-rollups-to-other-protocols"></sup></h2>