I have an online business so I know about this from both sides. I follow a lot of blogs. I also have my own blog tied into my business page, on which I sell things. I refuse to have annoying popup ads though.
It's a real balancing act. You want people to see you as a professional, bonafide business, but you also don't want to be annoying. You spend a lot of time creating content and you need to pay for the website/website developer, which makes it hard to just give content away.
I have taken online classes from people who have blogs I read. And I try to support the businesses with blogs I read, if at all possible. Sometimes it's just not feasible for one reason or another (US shipping costs and exchange rates for one thing). Other times the blog owner just isn't selling something I use, though the blog might be of interest to me.