Notice how the two players are forced to create meaning out of whatever they are presented with. The result, despite the difficulty, was not only clever but meaningful. The game is a lot of fun. Students love it, regardless of age. Adults love it too.
Some players are considerably better at it than others.
In general, people who do a lot of reading are quite good at the game. It makes sense, considering the large amount of syntactic and linguistic constructions such people are exposed to. The problem arises when one player attempts a legitimate construction that the second player simply hasn't learned yet. Consider the following example. Remember that the goal of the game is not to win but to write a poem.