It's a very difficult problem. I hear from these folks all the time who are law-abiding Canadians. Some are so-called accidental Americans; maybe their parents were there on vacation. Anyhow they don't owe any U.S. taxes, but they may owe hundreds of thousands or potentially millions of dollars in penalties. That's the worst part of FATCA, I think.
On February 14th, 2013. See this statement in context.