Public data upload price is planned to be 25% of private data upload price. After thinking about it for some time, I don’t think charging differently is a good idea for the following reasons:
One of SAFE’s main goals is providing us with digital privacy. More expensive private data prices gives people on a tight budget the incentive to upload their personal data as public data. We’ll essentially be in the same situation as we are right now, where people use services that destroy privacy because they are cheaper (free).
In the end, the network has to make sure that it’s expenditures are equal to it’s income. A 75% discount on public data is essentially a subsidy which has to be paid for by something else. Since expenditures (farming rewards) are a given due to SAFE’s independent farming rate algorithm, the subsidy on public data will be paid for with a higher private data price.
Imagine the network needs to have an income of 1 million SafeCoins over a certain period of time to be able to sustain it’s farming rewards. In other words, the network will set the upload prices in such a way that:
Public data income + Private data income = 1 million SafeCoins.
Let’s assume that an equal amount of private and public data is uploaded, which together equals (for simplicity) 1 terabyte (a million megabytes). So 0.5 TB + 0.5 TB results in an income of 1 million SafeCoins. If prices are the same for both types of data, this means 1 SafeCoin per MB. If however public data prices are 25% of private data prices, this results in 0.4 SafeCoins per MB for public data, and 1.6 SafeCoins per MB for private data:
(500K * 0.4) + (500K * 1.6) = 1 million SafeCoins
However, I think it’s likely there’ll be a lot more public than private data on SAFE, because most people create data to share it with others. If for example people upload nine times as much public data as private data to SAFE, we get this:
(900K * 0.77) + (100K * 3.08) = 1 million SafeCoins
Compared to the situation where there is no price difference, we now only get a discount of 23% on public data, and we pay more than 3 times as much for private data! This would be quite bad for SAFE’s competitiveness on private data.
In addition to the above, people may try to game this rule by asymetrically encrypting their chunks with their private key before symetric self-encryption is applied, after which they upload it as public data (un-encrypted datamap). This undermines the goal of the price difference between private and public data, and destroys the network’s ability to de-duplicate this data. In addition, this public-private data is less secure than real private data.
I doubt there is a way for vaults to detect this*, but even if there is, it means a bigger workload for vaults and additional code and complexity. If there isn’t, people will use this exploit (honestly, I would make an app for this myself), so a larger percentage of the network’s data will be “public”, which will aggravate the Economical effect described earlier.
*I assume that the vauls normally recognise data as public if a valid (matching hashes) datamap is provided by the uploader.
If we want to encourage people to share data to foster public knowledge and resources, I think it’s a better idea to intensify the GET-popularity reward scheme than to give a discount on public data uploads. It doesn’t have the bad side effects described above, and as a plus it only rewards data that is actually popular, which is probably the best metric we have for usefulness of data.
Regardless, different prices for uploading public and private data seems like a bad idea to me. I hope that we either scratch that plan or that someone can prove the arguments in this post wrong.