Depends.  If you're buying Bitcoin as an investment, this makes sense.  If you planned on spending your Bitcoin on a regular basis (using it as a currency, which is the whole point), just be prepared to report all liquidations to the IRS (even coffee).  Will they find out about small transactions?  Probably not.  Larger ones may attract their attention.  Be careful who you brag to, because the IRS is now giving cash rewards to people who report "tax cheats".  Also, if you play around on a non-US exchange like Bitstamp, you would be foolish to assume the IRS doesn't already have a list of US traders who have gone through the account verification process.  If there's one government institution you do not want to mess with, it is the IRS.

Sidenote, whether or not FATCA applies to foreign Bitcoin exchanges is still in limbo.  This will probably be resolved in the first round of Bitcoin IRS audits coming down the pipe.