I've been interested in this for a long while especially in memory models for forgetting patterns beyond simplistic SR expanding schedules.
We developed http://membean.com that utilizes some of this technology and we've been able to make this a successful business albeit in a restricted domain. But as others have pointed out .. it's hard to sell this. We've managed it because of stellar content built around our engine: http://membean.com/exemplars. Without excellent content it would have been hard to get this off the ground despite us able to show that we outperform existing SRS tools.
You bring up a good point. Perhaps targeting a specific demographic would make the sell a bit easier?
I don't think it occurs to many people to seek out and use memory tools. However, there are groups of people who do have a very specific need for these tools and actively seek them out. I'm thinking of people like medical students, language enthusiasts, etc... Anyone who has an immediate need to learn and recall large amounts of information.
By intentionally limiting the scope of what you offer, you can better target prospects and tailor your offer to fit their needs like a glove.
As you pointed out, the quality of decks is important. Limiting scope allows for creation of quality decks. At the end of the day spacing is just one aspect of forgetting - strong encoding is the other and for that you need rich varied content. Creating quality content is hard work. We started off with a focus on algorithms and engines and then realized that even if we slap the very best Memory engine if you have crappy content - no one cares (and retention is marginal over simplistic flash cards). We invested a lot of work on content and varied encoding and it's paid off and we are now branching into different verticals.
We developed http://membean.com that utilizes some of this technology and we've been able to make this a successful business albeit in a restricted domain. But as others have pointed out .. it's hard to sell this. We've managed it because of stellar content built around our engine: http://membean.com/exemplars. Without excellent content it would have been hard to get this off the ground despite us able to show that we outperform existing SRS tools.
Most recently Smart.fm tried this and failed.