I think I'd have to agree with you now: REST APIs seem to help with adoption. LogCabin was initially created for use with RAMCloud ( http://ramcloud.stanford.edu ), which mostly hand-rolls its RPC serialization to achieve its extreme performance goals (it budgets about 1 microsecond in software overhead per RPC). I thought I was being user-friendly in LogCabin by using protobufs, and at the time, something as embarrassingly slow as HTTP+JSON was unthinkable. I don't think it's too late to add a REST API to LogCabin, and it'd be pretty easy to make a REST proxy. Maybe that's worth doing for easier adoption from other languages. I also think the CLI client makes the barrier to entry pretty low for people that just want to test it out.
Tons of people are super comfortable with HTTP and have tooling built around testing and debugging it, even if the performance is crappier.
It's an ugly cousin of premature optimization that you have to deal with if you're producing APIs for your software. If the API requires anything that isn't braindead simple, you are going to lose out to competitors due to the learning curve.
