Apparently there were 214,000 people who complained about robo callers to the FCC last year. If you think about how obscure that reporting process is and extrapolate to the real number, you're probably not that far from the truth.
I've thought of making an app to automate the process. It would remember all form's entries for you (name, address, etc) and fill in the current time and date. You'd just have to copy the phone number.
Think there's any demand for this?