Personal blogs generally suck for the simple fact that most people's lives aren't really that interesting. And the ones who have interesting lives often aren't very good at articulating the stories to make them very interesting. I find these kinds of blogs to be great for making friends and very bad for making money. That is my experience.
If people want to build blogs that actually make money, I would tell them to first identify something that people would want to visit a site for. Find the demand first. Then go build a site to satisfy that demand. That usually means building a hobby blog or some kind of niche blog. Just make sure you start out with the intention to build an authority blog rather than an old school crappy niche site.
When it comes to personal blogs, unless you have some very interesting stories to tell and you can tell them in an interesting way, then you are going to find that hardly anyone wants to read what you wrote.
If your
life story truly is interesting and you have a magnetic personality that comes through in your writing, then yes you can be successful. A good example is
Heather Armstrong's blog Dooce. But people like her are rare exceptions to the rule.