Dan nailed it:
The second major challenge comes with performance, the Akasha DAPP will be competing with all other DAPPs for a share of the 20-30 tps that Eth has demonstrated on their test net. I am sure performance will increase and may be able to hit the 250 tps required for reddit scale. Social media transactions will be competing with financial transactions which will bid up the cost of both.
Steem is an almost perfect example of a standalone app with not much interconnectivity potential which gains nothing from being forced to share a slow network.
IPFS is interesting as the persistence layer. Where is everything currently stored for steem?
Everything is stored on the block chain, but could easily move to IPFS in the future.
Seems like it should be a priority.
I'm guessing it is a straightforward patch to force all content to be an IPFS hash. I think there are some working http gateways for images, and the official full node could pin everything. It seems really critical to get this done, unless witness nodes can already prune content - but there's no reason to reinvent decentralized content addressing for this.