[Cthulhu_]

Plus, Craigslist couldn't just change their design to something "modern", it'd put people off - people don't like change. Or, people don't like sudden change.

It reminds me of a national adverts website over here, Marktplaats; it used to be a very 90's, table-driven lists of links kind of deal with a fugly brown background. But it took off nevertheless, and became a major business that was eventually taken over by Ebay (in 2004). It's very slowly changed its front-end to a more modern facing one. But they made sure to do it slowly. Evolution rather than revolution.