It doesn't have to be about Marketing, Communications, Advertising, PR or how to start a business, it could be about one of your hobbies or another personal area of interest, but go ahead and start a Blog now.
While this may run counter to the general thought that you should have some kind of strategy and plan in place for how to roll it out, how frequently to update it and some thoughts around an editorial or publishing calendar, the sooner you start putting your thoughts down and publishing them to the world, the sooner you will be able to embrace and understand the power of these channels.
Take 90 seconds and watch this video of Tom Peters (In Search of Excellence and Re-Imagine) and Seth Godin (Purple Cow and Tribes) talking about why Blogging still matters and why you need to start writing one now: American Express - Open Forum - Let's Hear It For The Blog.
In this case, it sounds like planning is overrated. You're a smart person, you have something to say (about something).
Right now, most people are thinking about a few major things: Thanksgiving, the Holidays, the economy, the gifts they need to buy, the craziness in Mumbai and more. Nothing is getting easier, in fact - on the business side - things might start getting very complicated. We are already seeing major layoffs and the start of some scary big businesses (and small ones too) closing.
Do you think that the only people affected by layoffs and bankruptcy are people who are not as smart as you are? Doubtful.
No matter what other channels exist (Twitter, Facebook, LinkedIn, MySpace, etc...), nothing demonstrates who you are and what you do quite like a Blog. The reason to start one right now is because tomorrow may be too late. While a Blog may not replace the resume or a corporate brochure or a white paper, none of those will ever be able to demonstrate the one thing that truly separates you from everybody else: you - as an individual. Human beings are like snowflakes (no two snowflakes are alike) and, in a world where differentiation and uniqueness seems to be the only competitive advantage, nothing will demonstrate this more effectively than a Blog.
They're also very cheap (to get started).
In fact, you can head over to Blogger or WordPress and start your own web-based Blog for free in about five minutes. If you start there and you really enjoy it and you're building some kind of community and connection with readers, then you can splurge for a more serious software package, hosting, custom design, etc... Starting on the free platforms isn't the ideal way to really grow your Blog and bring it to the masses, but it's the perfect place to play and experiment with your voice and content.
Don't worry about how many comments you get.
It is always nice to be validated with comments and to use your Blog as a space to build a community (that's what this is), but having no comments does not mean that nobody is reading or that the content you are creating doesn't have huge value. Keep at it, promote it and let people know where they can learn more about you.
One last question: what are you waiting for?