Argument in which evidence presented in response to a specific claim is dismissed and some other (often greater) evidence is demanded.
This phrase is a straightforward derivation from sports that use goalposts, such as football. The figurative use alludes to the perceived unfairness in changing the goal one is trying to achieve after the process one is engaged in (e.g. a game of football) has already started.
Where are the transitional fossils?
Also known as raising the bar, it is immensely popular with creationists, this fallacy is used when a person has no intention of changing their mind about a position, no matter the evidence presented against the position or in favor of a differing position.
This tactic is commonly used in bullying, as well, causing no-win situations for victims in order to rationalize the bullying taking place.
In business, this is known as scope creep, where desired features of a product are continually added or modified leading to a perpetually unfinished project.