Keep getting a call saying this is the IRS Criminal Investigation Unit.  I called back one day and the person answered the phone, "Hello".  I asked who it was and then he went into his spiel.  

Person has been calling me from 1-202-609-7049 and claiming to be from irs investigators.I called it back and he would not say why!????

A caution from the *real* IRS, excerpted:

WASHINGTON — The Internal Revenue Service today warned consumers about a sophisticated phone scam targeting taxpayers, including recent immigrants, throughout the country.

Victims are told they owe money to the IRS and it must be paid promptly through a pre-loaded debit card or wire transfer. If the victim refuses to cooperate, they are then threatened with arrest, deportation or suspension of a business or driver’s license. In many cases, the caller becomes hostile and insulting.

... "Rest assured, we do not and will not ask for credit card numbers over the phone, nor request a pre-paid debit card or wire transfer,” says IRS Acting Commissioner Danny Werfel. .... Werfel noted that the first IRS contact with taxpayers on a tax issue is likely to occur via mail.

source: "IRS Warns of Pervasive Telephone Scam" - 31 Oct 2013
http://www.irs.gov/uac/Newsroom/IRS-Warns-of-Pervasive-Telephone-Scam


The FTC has issued similar warnings twice this Spring:

"Tax season may be over, but scammers posing as IRS officials continue to call, saying people owe taxes and better pay up. .... The IRS doesn’t ask people to pay with prepaid debit cards or wire transfers, and doesn’t ask for credit card numbers over the phone."

source: "Scammers continuing to pose as IRS agents" - 29 May 2014
http://www.consumer.ftc.gov/blog/scammers-continuing-pose-irs-agents

I got a call saying something like the "IRS has pressed serious allegations against your name"
Is it a scam?!

Short answer: Yes. Long answer: Did you read the post above yours? Answer is there to see.