Further imagine that everything you've ever drawn or painted—even bar napkin sketches, canvases you've painted over, torn-up first drafts and designs—you keep in the same room in your house. You keep the good stuff there, too, but it goes without saying that the incomplete works far outnumber the completed ones.
Now imagine that, somewhere in the mid-90s, everyone on Earth could instantly go into that room whenever they wanted and browse through all your material, finished and un-.
That's how the Internet works; everthing you've ever committed to its more-or-less infinite memory is still there. Blog posts you've taken down are probably cached somewhere, as are defunct websites, message board threads, self-published short stories/novels, and the like. Writers need to be mindful of what they post on the Internet—not only because that material, no matter how rough or polished it may be, reflects on their abilities as writers, but because as we move further into the Age of the E-Book, more and more publishers and literary magazines are considering work that appears on-line "published," and therefore either ineligible for submission or subject to copyright restriction.
The good news is that, unlike in decades past, it's relatively easy to reach an extraordinarily large audience. As long as you're careful about what you post, send via e-mail, comment on, &c, you can pretty much go nuts with building a (hopefully successful) media platform for yourself in the comfort of your own living room. Blog it up, post small excerpts (if you have an agent, be sure to consult him or her), self-publish if that's your thing (though we all know how I feel about it), and tweet to your hearts' content. Just know that everything you say is, effectively, on the record.
Tomorrow: guest post contest results!