Lobsters is invitation only: you have to find someone willing to sponsor you and your sponsor's reputation is tied to yours. In fact, the entire tree of sponsors is public. So people aren't just going to sponsor a stranger, and ostensibly people who use the site are well-behaved due to potential reputational impacts to both themselves and their sponsor if they misbehave.

In my humble opinion someone who went through all the trouble to get access and maintain it is far more likely to switch browsers to stay on the site. Then again I'm just guessing because I don't have access to lobsters myself! Perhaps it's just projection on my part.