Useless.. it doesn't work, period. Right after I visit some websites, Facebook floods me with ads about those topics...

It seemed to be working better before. I went on FB today, ( I rarely do) and it had clearly tracked me all along.

R9AN70HLEMJ

Using Facebook Container many times a week for about 6 months now. On a crowded up-to-date Firefox Nightly with Conex, Tree Style Tabs and other add-ons. Honnestly works almost flawlessly :-)
PS One can check if FC lets cookies alive in FF's Settings or using a privacy extension.