No one is asking you to provide an answer to all your profile questions (about drinking, religion, smoking, health, etc.) It sure looks like the data collected could be sold to health insurance companies, if you answered all these questions. Just don't, or lie.
No one checks if you provide correct answers - I guess many people lie about their age, drinking habits or whether they are married or not.
No one checks if your profile is fake or real.
Sure there's a bit of data mining to detect fraudsters, people creating lots of fake profiles or posting illegal stuff (porn videos), but it has nothing to do with "Federal data mining". And sure, your data might be sold to 3rd party vendors but you can create a bare profile, not joining, or deleting your profile.
Indeed, the biggest problem is not so much about privacy, but about spam / fraud and fake profiles used for marketing or doing illegal activity such as proselytism (think about extreme ideologies and recruiting people for violent actions - terrorism, racism, etc.), or sexual offenders praying on kids. The most advanced data mining techniques are designed to detect and stop this undesirable activity. And it's not done by government agencies, but by Facebook. Sure, the government is spending time on Facebook, but privacy invasions by government employees were much more severe during the census 2010 - remember all the questions you had to answer, e.g. about rare diseases? -- yet nobody complained about it, except me, and you were FORCED to answer or risk a $5,000 fine ( read my post) .
Also there's so many profiles that what data mining does is aggregating data in large buckets. Data mining could also targets the right ads for you at the right time, but to this time these algorithms are not working. A real risk though, is applying for a job and then a recruiter finding your profile and turning you down because of what you post. You could be denied a loan for the same reason as well. But for now, the gathering of such information is not yet automated, it's not data mining (yet). Then again, think about what you write, be careful, and you will avoid many problems. Facebook is a public place just like your workplace. Don't do on Facebook what you wouldn't do in your workplace.