I had a series of spam calls a year or two ago where the caller's number was the same area code and first three digits as mine. At one point I even got a call from an irate Mexican woman who claimed I'd just made one of these calls to her. I guess the telemarketers figured out people are more likely to answer calls that look like they'really local, even if they don't recognize the number, and they had some way of spoofing it.