Firstly I've got to thank Rod for using me as an example of someone bulding a personal brand - coming from someone with the personal cachet of him, it's a real compliment.
Both Rod and Don have alluded to the difficulties in being a public face. Rod due to his stutter and Don due to his unassuming nature. I sympathise with both of them - I also have issues that make it uncomfortable for me to "work a room" or give a presentation and it's something that I'm still not as good at as I could be - but the power of the internet is a real help for issues like there. Before having to speak in public under my guise of "SaaS commentator", I'd put in a year or so of heavy blogging and virtual communication making me somewhat more comfortable in my subject. As don said;
However, find audiences that you can relate to and start talking. It has to be done. No-one else is speaking for you. No-one can really tell your story better than you can.
There's no replacement for actually doing it however and I have t concur with Rod's view that you've just got to get out there and say your piece. I've been lashed in public by other commentators and by industry people who disagreed with my viewpoint - sure it hurts when those criticisms become personal - but it's all part of building a personal brand.
So yeah, get out there and do it... it's never abad as you'd expect!