How will the super massive black hole affect our galaxy? I've recently learned that the general consensus is that several (if not, most) galaxies have super massive black holes in their center, in particular the Milky Way. This, at least to me, makes perfect sense seeing as we are in a spiral galaxy which means we need something to "spiral" around (a large body or a bunch of mass).
But seeing as we're rotating around this massive black hole, won't we inevitably end up sucked in by it? Aren't we spinning towards the center of the galaxy, or are we staying steady where we are?
 A: It is a supermassive black hole but its mass is nothing compared to the mass of the whole galaxy. So if you remove the black hole, we will not feel any difference because we are so far away. It is not the central black hole that keeps the galaxy together, our sun is orbiting around the center of mass of the galaxy and the supermassive black hole just happens to be there(for reasons we don't fully understand yet)
If you are not very close to the black hole like in the inner parts of the accretion disk, it is just another mass to you. it won't matter if it is a black hole or a massive star.
However, there is some strong evidence which lead many astrophysicists to believe that supermassive black holes play an important role in the evolution (or maybe even birth) of galaxies. There seems to be a correlation between supermassive black hole masses and sigma velocities of stars in the galaxy. 
Wikipedia has good references on this M-Sigma relation.
A: Look at the question a different way: will the Earth get "sucking into" the sun? Answer: no, it's in orbit.
Now, black holes are a little different because inside 3/2 of the Schwartchild radius there are no stable orbits, but at very large distances gravity is gravity and orbits are orbits.
