What is dark matter? Well, we know what it's probably not: black holes. Astronomy Chair, Avi Loeb, and several colleagues decided to test the idea whether or not smallish black holes could be the source of the universe's dark matter, and Time Magazine's Michael Lemonick has written an excellent overview of their conclusions.
Full URL of the Time article: http://science.time.com/2013/09/05/the-mystery-of-dark-matter-clarified-a-little/#ixzz2ePZ0SHum
You can also download the original article coauthored by Avi and Paolo Pani here: http://arxiv.org/pdf/1307.5176.pdf