Thats a question that will be discussed when safecoin is being implemented. There was suggestion above that the costs will be different between writing to an existing MD and creating one. Also the suggestion was that there might be a difference between writing a small piece of data to writing 1MB of data.
I am getting the impression that this drive for appendable data is viewing the storage of PUBLIC files/data such as web data/sites and the desire to prevent the public being disadvantaged by deletion/changing of data they previous saw. Plus the fundamental of perpetual data. That is all well and good and I support it for public data/files. But the issue around private data is ignored above and the equating of perpetual data and appendable data as if appending is the only solution.
Unfortunately it seems that the debate is being reduced to this view of SAFE’s data and valid concerns around other areas is being trivialised. Now maybe this is a focus for alpha 4 (Maxwell) and a way to expedite that. Unfortunately if appendable data is the only way then it is going to cause a lot of problems for a lot of applications and speed. And the adoption of SAFE by 90% of businesses which is where the money is when they start storing the massive amounts of data they keep in data collections/warehouses.