There was a recent idea that small, primordial black holes might be related to dark matter http://www.nasa.gov/feature/goddard/2016/nasa-scientist-suggests-poss

There was a recent idea that small, primordial black holes might be related to dark matter http://www.nasa.gov/feature/goddard/2016/nasa-scientist-suggests-possible-link-between-primordial-black-holes-and-dark-matter http://www.nasa.gov/feature/goddard/2016/nasa-scientist-sugg... Basically the idea that theyre smaller and more common than previously expected - it would be really hard to observe them if they weren't in-between us and something else or snacking on something.