It works very well for Wikipedia though, but that's because Wikipedia has much more people that care about the information and maintain it. Google Maps lacks that community feeling of providing correct information, probably because it's owned and operated by Google.

Maybe local business organizations can provide help in this, have a few people dedicate some of their time to making sure all listings are correct. Alternatively, counties / local governments could take this responsibility upon them; after all, local governments dislike seeing local businesses go out of business or get less customers because they can't be found on Google.

At the same time, Google could do better in verifying changes; cross-check them with official address books and business registries and the like.