What would you normally expect of a graph-generation library? I'm talking about the pie charts, bar charts etc. You would normally expect an output to some file format, it being PNG or SVG if you're lucky. BUT, gchartrb doesn't do this, it creates a URL that you would use to GET the graph from the Google charts API.
Well, it's interesting because it means that some people at least consider that generating the graph using a REST API is as reliable as disk, and as convenient as a local library. I've used Google charts before, but I've never thought about integrating it into another program as a service, and I think it's pretty neat. And easy.
I'm placing my chips on REST.