I received a message on my answering machine today 03/30/15. Person with an accent stated that they were from the IRS and if I didn't return there call that there would be a warrant for my arrest. I called back to let them know that they're idiots the IRS never contacts you by phone and the individual hung up on me.
I got this call too on 3/31/15 - but my phone log indicated it was from the US Government number 301-729-6397 leaving no message on my answering machine (I heard the threat on PhonePower today 4/9) - and when I called the number on my phone log, it did indeed seem to be US Govt but did not take messages and told me to find my local IRS office and/or send emails that did NOT contain SSN or other similar identifying information.