We had a similar situation come up with one of our older products. People copied our initial hardware designs some 12 years ago, built (crappy) knock offs and sold them as their own along with copies of our chips to go along with it. The black market was clearly going to run us out of business and I despised the idea of having to basically compete with ourselves just to keep handing new features over to leeches. It was infuriating to the point that I had seriously considered just shutting the business down and moving on to other things.
Instead, we spent a LOT of time redesigning our stuff to prevent anyone from (reasonably) being able to do that again. We basically wasted an entire year just dealing with counterfeit issue rather than improving our core product.
Luckily it paid off and we were able to shut that whole black market segment down. But at one point we had to consider the same option FTDI did. We gave thought to effectively bricking devices that we were able to identify as counterfeit or, worse, someone would send us one of these counterfeit packages asking us for support or service on the item. We had to basically return to them a chip and adapter we knew, without a doubt, was a bogus copy of our stuff.
It was hard, but we knew full well we could not possibly damage or keep something they had purchased through what they considered legitimate channels. FTDI should have realized this as well. They royally screwed up on this one.
It's a little strange, though, because if you buy something somewhere and it ends up being a stolen item, you're obligated to give it back to the original owner. I mean the police trail leads to your doorstep, you're out the item you bought whether you knew it was stolen or not. I guess the same concept doesn't applied to IP somehow. I'm not even sure how it would. I guess IP isn't really "property" after all.