The correct answer to "Nine out of ten Americans already file their taxes on the Internet. What are you waiting for?" is:
It is a type of Bandwagon fallacy.
The bandwagon fallacy is a fallacy based on the statement that the opinion of the majority is always valid, as if everybody does it, you should do it too.
Comes from latin<em> Argumentum ad populum </em>which literally means "appeal to the people".
