A basic principle of social psychology is the "mere exposure effect." Developed by Robert Zajonc and others, this principle states that the more we are exposed to something (or someone), the more we develop positive attitudes toward it. "Familiarity breeds liking more than contempt. Things grow on us and we acquire tastes for things over time and repeated exposure (cite)"
The evidence for the mere exposure effect is convincing... In 1968, Zajonc (JPSP) did a study randomly showing people various Chinese characters and asking them to guess the meaning of the character. The more often respondents saw a character, the more positive the meaning they attributed to it.
This logic has been applied to advertising (show the product over and over) and to love (we become more attracted to people who we see more often). Let's apply this to blogging. What is blogging other than making others more familiar with who we are, what we think, what we're doing? As such, the mere act of blogging should make us more likable to others. If you blog, you should be more liked by more people than if you don't blog; furthermore, blogging should make people who already know you like you all the more.
This explains why, for me at least, most bloggers seem to be pretty likable people. It can also explain the popularity of blogging networks. Blogging should foster a sense of community—the more that we interact with someone, the more we like them, the more we want to interact with them.
This also explains why blogging advice often calls for posting photographs of ourselves. (For an example, and good advice about blogging in general). E.g., the photo above may be a desparate attempt to invoke the mere exposure effect.