Plus, if you don't cut them before you press them out, they can hog out the knurl in the hub and any studs pressed through in the future may be loose, allowing them to spin if someone hits them with an impact wrench.
A swedge cutter used to be a tool that every brake mechanic had in his box. Most people don't even know what one is anymore.
Here is a decent article that shows what we're talking about:
http://www.classictrucks.com/tech/0805clt_1967_dodge_truck_brakes_dodgeing_disaster/index1.html
