This is a significant scientific discovery, as it has implications for the evolution of galaxies. According to the paper and reports on this, these monster black holes are massive, bigger than we thought. Of course, it adds a bit of truth to saying "the bigger the galaxy, the bigger the black hole."

References:

Lemonick, Michael D. 2011. "The Blackest Black Hole: Scientists Find a Monster the Size of 21 Billion Suns." TIME Magazine. http://www.time.com/time/health/article/0,8599,2101916,00.html
McConnell, Nicholas J.; Ma, Chung-Pei; Gebhardt, Karl; Wright, Shelley A.; Murphy, Jeremy D.; Lauer, Tod R.; Graham, James R.; Richstone, Douglas O. 2011. "Two ten-billion-solar-mass black holes at the centres of giant elliptical galaxies." Nature, volume 480, 7 December 2011. http://arxiv.org/PS_cache/arxiv/pdf/1112/1112.1078v1.pdf
Overbye, Dennis. 2011. "Astronomers Find Biggest Black Holes Yet." New York Times. 5 December, 2011. http://www.nytimes.com/2011/12/06/science/space/astronomers-find-biggest-blac...