I can tell you from first-hand experience that they know what they're doing. They measure almost everything, nicely put together in dashboards with all the KPI's for the appropriate managers.

I think it's unlikely they used a suboptimal performance indicator to judge the site's new design, and would say the same thing about craigslist.

If only they would measure amount of spam in their for rent listing that currently nearly useless.

Remember, if the numbers don't support your opinion, it's because your measuring the wrong thing!