Thoughts? Would this be doable/practical/feasible/useful?
(...You didn't say how many separately-sited copies of your data dropbox's offer is/contains/represents...)
Okay, I have spent the night digging back into the details of various actually currently working software that I could run, but as you did not indicate what operating system you plan to use to provide the storage you are at least hypothetically offering I do not know if you could run them.
I am finding so far only two systems I actually have managed to get installed and working that seem like one or more of them of them might suffice for an offer such as is quoted above.
That is, putting aside all the theory and vapourware-wishlists and philosophy and looking at that specific offer as a potentially-tangible offer.
Those two systems are GNUnet, which currently requires a unix-type operating system to run, and Tahoe-LAFS, which is python and seems to think it is usable even on Windows.
Part of the differences between them is that GNUnet is not only about storage, so it has the "overhead" of trying to provide some anonymity. Requests sent out do not have to originate at the node your node receives them from, and nodes deliberately keep packets moving as background noise all the time so that timing attacks cannot notice aha look that node talked to that one, without having heard from another one recently, so I bet it originated that request itself.
So if you do not want anonymous routing going on, Tahoe-LAFS seems cheaper in resources to use as provider, provided your customers don't want the kind of anonymity GNUnet adds into the service-offering.
However, Tahoe-LAFS is organised as "grids", each "grid" being basically the collection of nodes a particular "introducer node" is able to introduce clients to. So in order to offer a Tahoe-LAFS based service you'd either have to have a few machines, probably best not all being in one site; or a number of us would have to team up to make one or more "grids" we would between however many of us be able to populate with enough machines, at enough sites, to be able to present the services of our "grid" as a credible service-offering.
I suggest that if you wish to sell your $5/month offering we should maybe consider teaming up with a third person so we can have at least a three-sites grid running, and consider whether to each use the price shown in the quote, totalling $15/month for someone wanting all three of us to store that much data for them so they have three copies out on the grid; or consider charging slightly less per redundant copy located at separated locations.
Did you happen to notice how many separate sites how many copies of your data the $20/month commercial offer was offering?
Despite the "overhead" of the (possibly extraneous to many people) anonymity that GNUnet provides, I think we would be better advised to go with a GNUnet solution, partly because using Tahoe-LAFS we would be trying to compete very directly against commercial services.
I am thus thinking lets start small, using GNUnet, then as we get customers for that "value (of being anonymous) added" service, revisit the price per gigabyte per separately-sited copy we could offer and whether it would be worth our while at the rates trying to compete with the commercial services would force us to drop our prices to.
WIth GNUnet we not only get to have this "value adding" feature of the anonymity stuff, but also the "it runs itself" feature of quite possibly providing quite a lot of its participants enough offsite storage and anonymous packet routing just in node to node barter that we could all have a useful number of usefully stable offsite backups without having to sit down and figure out how much bitcoin to send each other at all. The system has the virtue that we can all have these things for ourselves by barter up to the point where someone wants to receive more service than they provide. Those people will become thereby the potential "customers" who might go shopping around among those of us who have stably, long term, reliably had service to spare that we can offer them.
Basically it should find out for us automatically who among us actually does have surplus available and who among us is suffering sufficient shortfall of provision to start thinking about spending some bitcoins having in a sense run out of actual service of their own to barter with.
With Tahoe-LAFS, not only are folks not anonymous but also we each have to jump through gosh knows what hoops to figure out how much of our resources which other person is consuming more of than we are consuming of their resources. The administrative overhead thus looks like it would be much higher not onlly for those actually providing service but also for those wanting to leech or buy service (the potential "customers" among the participants).
-MarkM-