Creating your own blog is about as easy as creating your own urine, and you're about as likely to find someone else interested in it...However, there are many popular blogs already in existence, and if you want people to think you're cool, you're probably better off claiming you were a "guest blogger" for one of them. Your average blog has so many guest bloggers and such a crappy search feature that nobody will ever be able to prove you wrong."
See especially the parodies. Personally I always sort of mumble it under my breath, with a half-apologetic shrug and ever-so-briefly overturned palm: "...well, and I'm a blogger too, you know, so a wireless connection would then be nice. But it's not essential, no..." Which is not to say it can't sometimes be a force for good, of course.