Slippery slope

Slippery slope also known as absurd extrapolation, thin edge of the wedge, domino fallacy or camel's nose is an informal fallacy which occurs when the conclusion of an argument relies on a supposed chain reaction, starting from a relatively insignificant first event, leading to a more significant event, and so forth, until an ultimate event take place, and there is no sufficient reason to think that the chain reaction will actually take place.

Examples

 * "we can not let our son leave the bedroom because if we do, he might want to leave our house. If he leaves home he might eventually want to leave the neighborhood. If he leaves the neighborhood, he can be hijacked and used as a slave in another country. Therefore we should keep our son locked in the bedroom."
 * If we allow creationism in schools, evangelists will have a foothold in the public schools and start indoctrinating our children into their religious dogma
 * If we allow school children to question evolution, this will cause them to doubt evolution's viability and may stunt their progress in science education, which may overall stunt science education and affect our country's competitive position in the global marketplace
 * (Actually used by Bill Nye in Feb 2014 debate with Ken Ham) - If we allow Ken Ham's view of science into the schools, it will negatively affect their ability to understand technology and negatively impact our country's competitive stature as a leader in technology

Formal example
Formally speaking this fallacy has the following structure:

A leads to B, then C, ... then ultimately Z!