Caused my browser to completely freeze shortly after loading the page and seeing what looked like some interaction heatmaps appear.

I'm using Firefox 31.0 x64 on Debian 7 (Wheezy) with kernel 3.15.0-rc4. All plugins are click to play on my browser. Intel i7-4770K. 32GB RAM. NVidia GTX 770 with 337.19 proprietary drivers.

I had to press back and wait for a minute until my browser processed the event and got me away from the page.