I use them on small game because I get them dirt cheap or at no cost. I once got 4 dozen MA-3's and Bodkins for $5 at a swap meet. Last year my buddy gave me 3 dozen more he got from an old bow deal.
I'm always on the lookout for cheap broadheads. Hunting groundhogs is my passion and go through several heads per summer. Just yesterday I shot a nice one with a MA-3 and lost the whole arrow down the G-hog hole. Cheap arrow, cheap head, not a problem.
I would not be afraid to use them on big game. The steel is somewhat soft, which typically means easily sharpened.