Each instance of the component will render a unique style tag, however any changes to that components children will update the tag in place. The way it operates is similar to webpack's style loader, although source maps are TBD.
If there was enough requests I could look into making a single style tag, however I've never understood the benefits so if someone was willing to detail then I'm all ears.
EDIT
Also, if you made this a smart component top level you could easily manage the children contents via flux yourself to create the single tag you seek.
I think this is meant to replicate the Angular 2 way of declaring component styles. It'd be nice if it morphed a single style tag as @tracker1 suggested. Good job otherwise!
Interesting concept. I'm not sure if this brings enough over webpack's options or things like aphrodite. Also, not sure if the component will create multiple style tags, or morph a single style tag in the header, which would probably be better.
It could be useful for reusable components.