He would show photos from listings of excessively large, poorly made mansions (or 'McMansions'). He'd point out all the design flaws, and architectural mistakes, then laugh at the excessive price tag.
Apart from the humour, it was super interesting. If I look at a picture of a house, there's no way I can notice water damage, mis-matched windows, or just shitty door placement.
I guess Zwillo is salty as it could lead to lower valuations.
[There's still a post up on 99% if you want to take a geez](http://99percentinvisible.org/episode/mcmansion-hell-devil-d...)