I contacted CrowdFlower by email and they claimed that " Someone managed to hack the system and is using CrowdFlower's number as their caller ID."
About an hour later I received another call (the 6th one) from 415-621-2343. They claimed to be from MBNA, but I was suspicious, although very good it felt like the caller may have been phishing for personal information -- asked for my email address (which I did not give) and asked for a secret password, suggesting that many people use their place of birth as password -- that seemed VERY suspicious to me. I refused to give any information.