Are some subsidies valid?

From, a project of Institute for Humane Studies:

Prof. Art Carden has developed some silly walks and is seeking payment for his work. Since he cannot find anyone to pay him voluntarily, perhaps he should apply for a government subsidy for producing silly walks. But while silly walks may benefit society, the fact that people will not pay for their development voluntarily indicates that people do not value silly walks as much as other things people would pay Prof. Carden to do. Are some subsidies valid, though? What about for food? Or for education? How about subsidies for clean energy? Is government assistance definitely better for society? What do you think?