The truth is, it's not as easy to carve out your space on the web and make a name for yourself as a blogger today, as it was back when blogging was brand new. And it takes a lot of time to build your audience to the point where it's successful. (The most successful, multi-million dollar blogs today were started around 2005 or earlier.) So it's definitely not something you can get rich quickly with, though many people do work on their blogs full time.
If you're passionate about a subject and you have decent writing skills, blogging definitely could be an alternative career path for you. The short answer is, yes, it is possible to make a living—a very good one, even—by writing online. On the other hand, the hard truth is most of the millions of bloggers today don't make enough to support themselves just with their blogs. Let's take a look at what's involved.