I think all you metallurgists are missing something. Brass is especially suited to ammunition use because it IS softer and can expand and then contract quickly after firing, allowing it to alternately completely fill (read: seal) the chamber, and then extract easily.
A case that stretches uniformly and somewhat easily is less likely to split than a case that is harder or more brittle. Indeed brass that has been reloaded several times becomes less safe because it gets work-hardened by being continually fire-formed and then resized. This causes it to be brittle and thus more prone to splitting. This is the reason neck sized rifle cases last much longer than full-length sized cases.
Has anyone seen the new 5.56 cartridges that are all plastic except the base? They work because other than the breechface there is nowhere for gases to go but out the muzzle. The case expanding makes no difference.
ETA: Ooops... IMHO this makes brass cases superior to steel, especially if you want to reload them! Steel is a throwaway for more reasons than one, but it should be fine for one firing.
I would also add that most people's aversion to Wolf has less to do with the case material and more to do with other issues directly related to consistency and quality of ALL of the components.
It works fine for me though...