Non-compliance has serious penalties, but the good news is that for late and non-filer expats the IRS has a procedure for low-risk taxpayers to catch up - without penalties - if they now voluntary file returns for the last 3 years and FBARs for the last 6 years.
Streamlined Filing Compliance Procedures Information from the IRS
Forbes Magazine (2013) wonders What To Say When (Not If) Your Offshore Bank Asks, 'Are You Compliant with IRS?'
Where do I start?
The IRS provides an overview of options for taxpayers trying to comply with filing, including nonfiled FBARs, low-risk filers and filing without owing taxes.
As always, please consult a tax professional for advice concerning your personal situation. (Be sure to understand the difference between consulting a tax lawyer and a tax preparer when making decisions about back filing using IRS compliance procedures etc !!)
For example, check out the American Citizens Abroad Expat Tax Services Directory when you need professional help.