On a related note, 50 and 100 dollar bills in New York City are generally not accepted in most stores due to counterfeiting. Many places also refuse them due to not having enough change.
This is a correct understanding, though the US bills have gotten harder to counterfeit in recent years with the addition of color shifting inks and 3-D security ribbons. I'm comfortable taking larger bills for craigslist stuff when I have a mini UV light and anti-counterfeit marker with me. Though I prefer to meet at the bank and immediately deposit in the ATM.