Sarcastic or not, it's an important point. You are giving up a significant attribute of your identity to the protection of a US technology company. Whether that bothers you (or not) depends on how much you value your privacy.
If they don't already have your fingerprints on file, which depending on where you live happens as a kid in case you go missing, get a drivers license, etc.
If the NSA wants to target you specifically, you're fucked no matter what unless you move to a cave. No point in being needlessly worried. I'm more worried about this causing someone to cut off my finger while stealing my phone than I am the NSA coming after me.
