About 12 million Americans keep blogs, according to a survey released last July by the Pew Internet and American Life Project. Even more people might blog if the technology weren't so public. After all, who wants to share a high-school-reunion video with stockbrokers in Istanbul or teenagers in Tokyo?

Privacy controls that let a blog's author decide who can view each post are a major feature of several new blogging platforms. Vox, a free Web-based service launched by the San Francisco blogging-software maker Six Apart, allows users to assign various privacy settings to each post. The software is free, but bloggers have to accept that an advertisement will follow each of their posts.