Breaking the grounding pin is also very common. Often these things are so flimsy they break off all by themselves when you pull the plug out of the socket (happens on power strips at work a few times when things get banged around).

It eventually compromises the mechanical integrity of the remaining contacts. (I don't understand your friend - those adapters are US$1 for a two-pack at the dollar stores in the city. Cheapskate? [Linked Image] ).

Most of the molded-on plugs I've seen have hollow grounding pins (cheaper to make?).

Aftermarket replacement grounding caps have pins made out of thick copper or brass bent in a sort of inverted U shape.

These are much more resistant to breakage and bending than what is essentially a hollow little copper or tin tube held in place by a blob of rubber or plastic (the plug top itself.

Has anyone seen a Nema 5-15 plug with a solid round earth pin?