Clue me in about Facebook comments (I'm considering using them on a current project). Why do you consider them a failure? I thought Like + comments was pretty

Clue me in about Facebook comments (I'm considering using them on a current project). Why do you consider them a failure? I thought Like + comments was pretty damned brilliant, because they make FB part of the infrastructure of so many sites. Plus, anecdotally, every time I turn around another site is rolling out the comments in a big way (like the LA Times recently did).