It's an analogy for "the super latest greatest startup web site" and how it's risky using it (aka moving in).

You don't pay for it, so you don't have any claim as a tenant when they decide to cash out.

He's talking about startups getting acquired and then shutting down (see the last link of his post referencing Posterous).

I could be wrong but I think this is a satire on what happened to Posterous, he's saying Posterous is the "landlord" and they built this "space" to work in for free; but they just did it with the intention of getting their name out there knowing that there would be an exit at some point. He feels betrayed b/c there was all of this trust built up and now they are closing down.

It was analogy, not to be taken literaly. Ragenwald wanted to say that free services (webpages, applications, etc) provided by startups often ends up after a while, and people depending on them are left hanging.

Indeed. Maybe it's actually a metaphor for cool free apps and what happens when the startup behind them gets acquired?