I don't think he seriously views Second Life as a real competitor - he was just using it to draw an analogy.
As for the community, I believe the "fakeness" he's getting at is the ability of the user to carefully cultivate their likeness and project a version of themselves that may or may not be truly reflective of "reality".
Of course, one could argue that we are always cultivating a "desired image" of ourselves. However, Facebook and similar platforms provide visual and textual clues that allow users to more concretely realize social relationships. This in turn may allow them to go above and beyond the normative level of image moderation. Whether that is "good" or "bad" is another question altogether.
Dvorak hates facebook because it allows people like Dvorak a soap box to stand on.
In reality, my friends, on facebook and in life, are not Dvoraks. They are normal people with jobs, with hobbies, etc... People (usually) too busy to worry about online image or rant about popular internet culture. That's why I like facebook. If I had a bunch of Dvoraks for friends, I'd probably hate it too.
There's nothing "fake" about the community on Facebook. Ask Hosni Mubarak.