FPAAs don't really exist as products you can buy, as far as I know (unlike FPGAs, which are a very mature technology to the point that I suspect there's nontrivial (say, >5%) odds the average HN reader owns something with a FPGA in it somewhere.))

I didn't know about this. It's curious that the article mentions that recently (2016) improved FPAAs were demonstrated. Perhaps an opportunity where there wasn't one before.