People who write those blogs might be selling something somewhere else. There may be an occasional link to someone else who is selling something. But with the best blogs, you can read them day after day and not feel like you’re getting pitched.
Seth’s blog, for example, has a couple links to other sites where he’s selling stuff. But even though he’s talking primarily about marketing, he’s not pitching his stuff in the posts. Mitch Joel and James Altucher also have this kind of blog.
Second tier bloggers have lots of great information and ideas on their blog. Good for them, and I read their stuff, too. But a second-tier blog mixes sales into their content. As in: “Here’s a great idea, and if you want to see more great ideas, sign up here.” Or: “Here’s something useful about [whatever], and as long as we’re talking about that, you might want to try this thing I’m selling.” Or, at the end of every post suggesting that I download their free e-book.
Then there’s the kind of blog that’s more about pitching the blogger’s stuff than the content, where posts are about getting you to sign up.
I’ve been blogging for years and I’ve never made any money. Some people seem to be able to make money at it. They seem to be the people who give advice about how to make money blogging. Not me. I haven’t made any money blogging, and I can’t sell anyone advice on how to do it. I don’t think the best bloggers are doing it for money either. They do it because they love to do it. They make their money doing something else.
Bottom line: the second you start blogging for the money, or because you want something from your readers, your blog will start to suck. Blog because you love to do it. Make your money doing something else.