[klipt]

Using adjectives as adverbs is incorrect in British English, but extremely common in American English. For example:

"I'm doing good" instead of "I'm doing well" "He eats real fast" instead of "He eats really quickly"

If enough people speak that way, I don't think you can call it "wrong" so much as a dialect in its own right.

[erikpukinskis]

I wouldn't correct a native speaker. I was just offering, in case they cared.

Fast and good are de facto adverbs. Maybe in some American dialects it's common to use other adjectives as adverbs, but not in mine.

Agree that language changes.