I was never talking about tagging data. Just vaults.
I’d say if you’re offering 1.2TB of your hard drive, you’re more dedicated than the average user already 
Anyway, let’s do the maths.
Under the assumption that distribution is initially random (in practice, it would probably shift towards large-scale commercial farmers pretty quickly, as they have 24/7 uptime and much larger bandwidth reserves than the average user), the total storage space on SAFE is 1 PB on day 1 (I mean, I’d love that too, but I think that’s quite an optimistic estimate), and you provide 100TB of space yourself:
When a chunk replica is uploaded, the probability of you not getting it is 100% minus your share of total storage space (as long as distribution is indeed random), so 90%. As 4 replicas are uploaded, the probability of you not getting a single one of them is 90%^4, so 65.61%.
So for every chunk uploaded, you have a 35% chance of getting at least one copy.
For a small file of 3 chunks, your probability of getting a full copy of it is then 35%^3, so roughly 4.2%, and the inverse, the probability of you not getting a full copy, is 95.8%.
Let’s say someone uploads 100 photos which all fit into 3 chunks each. The probability of you not getting at least one full file then is 95.8%^100, which is… about 1.37%.
@dirvine has stated that in practical tests this isn’t a problem, so I’m probably wrong somewhere, and I’d appreciate it if someone were to point out as to where. It’s not like I want this problem to be real
Getting slightly off topic here, but if you run a server farm, you don’t let a hard drive failure destroy your data 