Slaad farming? What a... bizarre... idea. Wouldn't work in my campaign, though, since I created a new type of slaad, the brown slaad, that results from implantation/infection of animals or immature creatures. Stunted, retarded little things that aren't good for much (and can't reproduce), but their smallness and weakness make them the only slaads suitable as Improved Familiars (I went on a bit of a familiar-monster-creating kick a while back).
There's also the fact that while slaad aren't very organized, and probably don't have much racial loyalty, sooner or later some slaad would probably come and free them if for no other reason than to see the glorious chaos that would result from hordes of its fellows being loosed on the material plane.