Rated 4 out of 5 stars
I really like the concept behind this add-on and overall it seems to work really well, but it is not without flaw. In less than 24 hours I've already found one site that does not like it.
With the add-on enabled, I cannot reply to topics on 4chan. Since linking to a previous page, from the same domain, this should not happen... and after disabling Smart Referer, the problem resolves itself.
So it seems like Smart Referer could use a little more tweaking or whitelist support. Beyond that, it seems like a great add-on and I'm looking forward to future releases.
Just disable strict mode, set extensions.smart-referer.strict to false.
Also the next version that is being reviewed will have whitelist support.