Although my libertarian leanings would raise no objections, I don't expect a blog to be called anything like "Bill's Gambling Tips" anytime soon.
Could subdomains ever raise a trademark question the way domain names have? I haven't heard of it happening, but in theory anything that interferes with another entity's branding in the same business category (as USPTO defines it) could raise questions.
Another tip: If you have a sci-fi script set on another world, make the world seem like something that could be modeled into a Las Vegas resort. (For instance, in my case, a railroad track built as a mobius strip.) I'm surprised no casino has been based on Clive Barker's "Imajica". Imagine a resort based on the Five Dominions (and pretty heathen, as in the First Dominion, man beats God). Or imagine one called "The Cibola", based on the name Stephen King gives Las Vegas in his novel/TV movie "The Stand".