Craigslist disrupted the classifieds industry because it had first-mover advantage in a new medium, the Internet. It now abuses that advantage in order to not innovate or even compete.
The market is not working over time -- proof is how everyone complains about how crappy Craigslist is.
But a solution, for example, could be something like: legislators could force companies with over, say, 25% market share, that are mainly based on user-generated content, to not be able to sue other companies if those companies re-display information originally input by users, that is publicly visible on the site.
This wouldn't force Craigslist to alter its behavior one bit. But it would allow entrepreneurs to actually fight once again on the basis of their ideas, as opposed to whoever had first-mover advantage and subsequent network lock-in.