So I'm just going to jump right in to the maths; My web host offers a server with 5x2TB drives, unmetered 1GB/s connection and can provision servers in 5 different data-centers, for ~$200/month.
If I got 3 of these servers and install OpenStack Swift on them, I have ~10TB (I know it'll be less than that but to keep the maths simple I'll just say 10TB) of storage with the same features as Rackspace Cloud but for $0.058/GB (Compared to $0.15/GB for Rackspace). Plus free, unlimited bandwidth. The servers could be provisioned in 3 different DCs for redundancy and for scaling new servers are active within an hour so we could scale up our storage reasonably quickly if we needed to. We'd also be using a CDN to deliver content, so yes there would be bandwidth charges but they would be external so irrelevant to the question.
Obviously it's only more effective if working with large amounts of storage (For, say 2GB it's a lot less efficient) but we have 7.5TB of backups on a RSC files account so our effective price per GB would be $0.078 (But that would decrease) compared to over $1000/month with our current Rackspace system.
So my question is, other than having to manage our own servers and putting a bit more effort into scaling, what's the difference between a self-managed storage system and something like Rackspace cloud, is it worth $/GB difference+bandwidth charges?