Here's a quick demonstration of how you can wind up tripped up by this:
It's payday, and it's one of those months when it comes just a few days after you've just paid your $1200 rent, so your checking account - which was on the borderline of being overdrawn - isn't empty (yay!). Together, you and your spouse got $3k net from your biweekly pay which went into your joint checking account. You're not rich, so you haven't thought about separate accounts to avoid things like FBAR.
Since 2009 you've put $500 a year in each of your two kids' RESP (education savings) accounts, and Canada matched 20%, so you've actually got $3k in each, and the assets have appreciated 15%, for $6,900 total. You've got signing authority on those, so they count towards your aggregate total.
Whoops, you just hit $10k! And you're thinking - WTF? I just got paid $3k and I have $6600 in the RESPs - that's not $10k! But your landlord didn't deposit your rent check yet because he's with his sick mother in Abitibi-Témiscamingue, so you're at $10,800.
Your last hope, of course, is the weak looney, and indeed, $10,800 Canadian is not currently worth $10k American. But on some days, it is, and you can get tripped up by exchange rates, too.
The point of this fun little exercise is a) to point out how easy it is to find yourself subject to these rules and b) how nonsensical the $10k threshold is as a policy matter. The US has created a burdensome and intrusive reporting requirement that is not widely known about, has draconian penalties, and affects people doing very normal things who are exceedingly unlikely to be engaging in the activity (financial crimes) the rules are trying to catch or prevent.
I know there are lots of young couples doing the immigrating, and $10k seems like quite a lot when you're younger (unless you've been on the receiving end of a $10k tuition bill in the US - then you're like, why so low?), but once you're just a tiny bit more established, with both of you working, you can find yourself at $10k pretty quickly, and the $10k is at any given moment in time during the year... even if it's just because your landlord deposited the rent check late...