Neither the OED (abridged) nor dictionary.com lists 'casted' as a word or proper form of a word. It is incorrect usage in all cases. The past tense of the word is 'cast,' whether you're talking about being placed in a role("Yay, I was cast as Treize!" "I cast him for his uniquely wide vocal range") or you're talking about throwing something ("The die is cast" or "He cast the interloper into the abyss"), or you're talking about producing something from a mold ("We cast only thirty widgets of that design. It shouldn't be hard to track down").
One of my happy moments is when people use it correctly, too. So I'm absolutely, 100% with you there.
POSITIVE: When people have obviously proofread their writing.