Recommendation engine as a service (http://savant-api.com/) -- absolutely nothing public yet, except a fancy d3 powered widget that has nothing to do with the service.
It's cool because I'm hoping to make collaborative filtered recommendations easy to obtain for small outfits.
Will your recommendation algorithm be public or secret? Will it be customizable by your users?
You mention a bulk import. Will you provide a bulk export, or will I have to keep my own backup database to avoid lock-in?
I see in your API example a bucket, a source, and a target. Would you consider a "value" field, for graphs with weighted edges? (The question is moot if I can't modify the recommendation algorithm to employ it.)
It'll use standard algorithms, although the MVP will only have one available (using pearson currently). My goal is to make various alogrithms eventually available, and perhaps some mechanism to select the best automatically (e.g., selecting the best method based on how sparse or dense the graph is).
As for bulk export, yes in the sense of "download all the calculated recommendations" (perhaps you want to dump that to a local db to access that data directly, rather than rely on hitting my api every time you need something), but not "download all the data exactly as I put it in". For the most part, the data you put into my service should already exist in your own database (what products your users have purchased, what products your users elected as liking). In addition, you'll likely want to use a one-way hash to hash sources (especially if you use usernames or email addresses to uniquely identify users).
I probably won't launch with the ability to add weights to edges, although that's probably one of the first post MVP features on my todo list.
It's cool because I'm hoping to make collaborative filtered recommendations easy to obtain for small outfits.