Steve posted an interesting editorial on blogs at http://www.sqlservercentral.com/forums/shwmessage.aspx?forumid=263&messageid=393904 and the follow up discussion was pretty interesting. Read that if you have time, but the short story was he recommended that you separate personal/professional blogs. Easy enough to understand why, but that really leads to a larger discussion of when/why blogs are useful.
Take my low key blog here. I would say it's clearly focused around my career and professional development, but it is useful to anyone besides me and perhaps a future employer/customer? Does it need to be any more than that? Very few us of have something compelling to say every day or even every week, or solve interesting problems all that often. Take a look at the blogs you read, are they really aggregating content (leading the way for you on a topic that interests you), maybe informational/vendor issued stuff such as you might find on the PSS blog, or are they thought leaders themselves, or are they just 'big names' that you read to see what they say? Probably other reasons too!
Of course the power of RSS is that you can throw the blog in your reader of choice and glance at it if something pops, doesn't take a lot of time - I certainly doubt you'd be reading this if you had to find in your favorites list for something to do!
Maybe over time I'll find 'my voice' and speak more consistently on a smaller set of topics. For now I'm interested in SQL of course, but often from a less technical and more business driven perspective, training and career development (I earn my living doing those), user groups (somewhat related to training), and being a bit entreprenuerial. I'm going to try to stay reasonably focused on those and just try to post consistently and see what evolves.