I received calls from this number today and this past Friday. No message left. Since I discovered on this site that others had received calls from the same number, I decided to block it.
I just got a call from 650.238.9972. I have several friends in the 650 area code - it includes the San Francisco area, parts of the old 415 - so it's plausible I could be getting a call from an unrecognized number. I researched the number instead of answering - I was in front of another computer at the time the call arrived - and found the helpful information here. The call was five minutes ago, and they do not appear to have left a voice mail.