You may think that the world doesn't need any more genealogy blogs, but here's a reason to start one:
A relative might contact you.
My recent postings on www.rootdig.com about my findings at the Family History Library in Salt Lake brought about a reply from a researcher in Scotland who descends from my wife's 4th great-grandparents. I searched for these ancestors in several online databases, all to no avail. Despite this lack of any luck, within two weeks of my posting about the family, there was an email in my inbox.
I'm not saying you have to blog every day, or even every week. Personally I'd rather do actual research and analyze what I have. But an occasional entry about what you have found might bring another relative out of the woodwork.
I use www.blogger.com for mine, but there are other sites /software that one can use.