What I kind of figured out is... if you're genuine, hitting on relevant topics to general interests, you'll get a few hits.
(Aka - youtube is a community, Share the love to get the love. If you're not active on other people's youtube pages, videos, commenting, sharing, favoriting, subscribing... you end up getting less hits than if you are active. Group channels will get bleed-over hits and subscribers, but it's up to YOU to keep them.)
If you're lucky AND genuine, you get picked up by other youtubers or get skyrocketed by a blogger/news site.
If you're just plain lucky (content or not) you go viral.