Using a grammar and a dictionary of common words I can see attacks on 3 or 4 word passwords being somewhat feasible although I should do some back of the envelope calculations.
There are roughly 32 billion of google 4-grams.
Summing up, a meaningful 4-word phrase, is, in the terminology of the article, "risky".
My advice: use generated passwords, and apps like 1password to remember them.