Sample Size! Sample Size! Sample Size!

When does the "Sample Size" argument become moot for various aspects of a player's hitting line? According to data summarized on Fangraphs.com (originally from this website),

50 PA: Swing %
100 PA: Contact Rate
150 PA: Strikeout Rate, Line Drive Rate, Pitches/PA
200 PA: Walk Rate, Groundball Rate, GB/FB
250 PA: Flyball Rate
300 PA: Home Run Rate, HR/FB
500 PA: OBP, SLG, OPS, 1B Rate, Popup Rate
550 PA: ISO

Cool stuff.