What's your mental image?

When we know one another using this series of tubes it leaves a great deal of room for mental interpretation of who we think we're talking to.

So, in honor of IBARW, I thought I would ask: What's your mental image? Barring any concrete knowledge of who you're dealing with out here on the internet, what do you tend to assume?

For the purposes of the poll let's read "talking to" as meaning "On Livejournal, or places like it." In other words, places where the assumption is not obvious. (As opposed to, say, a message board about being pregnant, where one would have reason to assume most folks were women)
( Poll ahoy! Though longish, so behind a cut. )