And also provide the least chance of getting caught. Yeah, I know it's anonymous, but at a small company "anonymous" doesn't mean much. It's not hard to figure out who's dissatisfied, who's the gossip queen/king, or even figure things out just by the way someone writes.
Vault.com, despite not having nearly as nice a site as overhear.us, had reams of traffic and posts about individual employers, until it got blacklisted.
I can imagine this site having a good following with companies that are not strict about the web-filtering list [which I abhor, btw].
However, those companies are not likely to be large because large companies have burdensome regulations [SEC in financial industry, HIPAA in healthcare industry, SarbOx for all public companies] that generally require (or imply that) employee communication and web usage should be monitored.
And large companies are the interesting ones for overhear.us, because they have the most interesting networks and stories!