Oh, dear Lord, that's the subject of some of our most intense internal disagreements. There are standards of notability, which like most standards are subject to interpretation; and there are always those who want to push the envelope one way or the other. I am of the evil tribe termed "deletionists" who think there's too much crap about recent nonsense; and believes in fewer but finer articles; ideally, reducing the total number of articles in the English-language Wikipedia from 2.7 million to 2 million or fewer.

The other tendency, of course, is referred to as "inclusionists." I don't know of any reliable indicator to predict which way any given person will lean, aside from a tendency for the youngest editors to think that any content that was on television after they were three is central to the knowledgebase of humanity.