When you choose to share your personal life in your writing there's an assumption that you've opened yourself up to a one-way critique by your audience. In some ways, that's true. My readers can form opinions about me based on what they read on my blog, pictures they see that I've posted, or things I've shared online might lead people to believe certain things about me.
The same could be said about the author of a memoir, an actor who's interviewed, or a celebrity photographed by the paparazzi.
However, bloggers have something at their disposal that an author of a memoir, an actor or a celebrity do not: blog statistics. Sounds boring, right? Not really.
Consider this scenario. I notice someone from company X has started to show an interest in reading my blog over the past few days. I can see which posts this person reads, how long she spends reading them, what she downloads, clicks out onto, what type of computer she's using, her browser type and version, her operating system, etc. If she clicks on my email link, I'll be notified. I'm also told how she found my site: Facebook, google search (what the search string was), an RSS feed, etc.
In this way, a blogger can learn a lot about their readers. It's what allows us to get to know the people who don't comment. We can use this information to mitigate situations with stalkers (as sometimes happens) or target ad campaigns (based on blog traffic). For example, there's been a huge rise in smartphone use in my stats over the past year. This means I need to be aware of my blog's formatting for mobile browsing. Stats are essential for observing both trends of individual browsers of a blog and the group's trends. I'm a keen observer of both.