(Flowtown's blog had 350K U/V month and drove most of our customers, Clarity is at 20K U/V month - using a different strategy for growth)
So I've done it a couple times now, and Sean is right - you want to talk with Hiten (KissMetrics) or Leo (BufferApp).
I'm assuming you want numbers - we'll here's the deal.
1. There's a real cost to the blog
2. It's getting increasingly hard to pull this off
3. You need an unfair advantage
One: I spent half my time managing the Flowtown blog, and $5-10K month on hiring writers and designers (infographics).
Two: With EVERYONE getting into content marketing thanks to amazing companies like HubSpot, it'll continue to get harder and harder to rank in SEO or get social media love.
Three: Everyone mentioned above/below (including myself) had somekind of unfair advantage. Maybe it was high ranking accounts on Digg.com / HackerNews / iTunes, or connections with the press to get distribution of top articles.
My only advice is yes it can work, but you need to treat it like any other paid marketing channel (cause there is a cost) and decide if it's the one you want to invest to the most.
The upside of a great blog is that it's an asset long term vs. paid ads that stop being displayed if you don't pay :).