1) Domain name publisher.
Pros: Actual people have done this and made money. Also, it's a reasonable model - you're scavenging the internet to find domain names, then selling your newly discovered treasure. Looks legal.
Cons: You may become attached to the domain name, the celebrity in question may attempt to sue you; even though the case would be without merit, you'd need a lawyer to make him shut up. You also have to pay for registering and hosting the domain.
Summary: Overall, not a bad idea.
2) Fake Cause
Pros: Would probably work, would be very entertaining, looks legal.
Cons: The real idea is to sell a product, the cause is just an elaborate marketing campaign. Developing the product could cost millions of dollars. It would be easier to encourage support for a political action committee, though perhaps not as profitable.
Summary: This is actually a brilliant idea, but could take over a decade to fully implement.
3) Failed Idea
Pros: we learn the costs of running a website; the article was very informative and will be useful for future HTMAD reference
Cons: it failed
Summary: Not much money to be made in anti-porn.
4) Red zeroes
Pros: This is kind of funny. Not quite illegal unless you steal the dollar.
Cons: This is little more than a joke. Sure it's low cost, and sure HTMAD posted a similar idea, but in reality, you will not fool anyone.
Summary: haha, no.
5) Gas Pump
Pros: Could potentially make money if it works.
Cons: Illegal, consumes too much time and energy. Also, how are you getting that gas pump to the gas station? Rent a truck? Camels? That will probably cost you some money. Will not fool anyone.
Summary: why even bother trying this?
So how to vote? Well, I, the Official Fact Check Guy, endorse #3 for completely failing to follow directions and embarrassing himself by talking about his failure in the process. Were it my dollar to give, though, I'd give it to the fake cause guy.