Sometimes it is just as easy to right-click and view the source of a page, but I find many things new when I use BuitlWith... I also was, at first, not that impressed with what BuitWith is doing as far as the model of their website resource User Experience; but once I started using it for what it is, I found many technologies that were very interesting to me that I would have otherwise just passed by or never found.
This plugin isn't working for me with Firefox 32.0.2. All I see is a blank white box with a "Close [x]" on any site I've tried. I know it worked with earlier version of FF and I absolutely dug it.
UPDATE 09/20/2014 - 1 day later: First, thanks to the developer for responding so quickly. Much appreciated.
It wasn't an injection (per se) or an https problem, or an incompatibility with the current version of FF. It was a tracking cookie blocker I'd installed a few weeks back. As I hadn't used BW since (evidently) I hadn't noticed it sooner.
The plugin is Privacy Badger (and it rocks). If you have it installed, or planning to you need to make sure that you "green light":
I suppose you could say there's an "injection" happening - PB injecting itself in the page load, but it was the developer's response that nudged me to think about what I may have installed since last use *because* I didn't want to spend hours turning off plugins and restarting. I should have thought about this first!
So again, kudos to the developer for a speedy response. Fixed just in time for some work!