>The key addition with Pilosa is that it's distributed and can scale horizontally :)

Doesn't this also make it several orders of magnitude slower? Every time I find myself using Bitmaps it's when speed is extremely important. What are some use cases for this not covered by in-process Bitmaps, Bloom filters, and HyperLogLog?

I'm just not aware of many use cases for bitmap indexes willing to trade that much speed for database-like access. I think this project would be more usable factored into a library than something external