I took the picture that is on velobase of a cracked death stem. At least I think its still up.
Sheldons reference has been previously disregaurded as a safty sentiment only. - if you don't know if its dangerous, you should replace it just to be careful.
Aside from this, I have only seen failure in the 2-slot versions. I use (and occasionaly inspect) an AVA stem with 25.4 clamp and one slot. Also I have never heard of the later "open-face" AVA stem having any issue.