If you want an example of company that crumbles under its weight because of code quality, look at Frendster.

Maybe you never heard about it, but it was the leading social network before MySpace then Facebook.

It was unable to scale, and as a consequence suffered bad performances and downtime and eventually all the users moved to more recent SN.

MySpace also had similar problems, their main app was an crappy ColdFusion app that they struggled to update to add features or fix bugs.

Facebook on the other hand, was far better technically and it's probably why they won the social network war.