Thanks for the responses everyone!
Is it me or does it seem like there's a huge discrepancy between US and non-US members? Not having to hit the minimum spend of $25,000 makes it seem ridiculously easy to get Diamond status. According to some quick calculations, I'm about $1700 worth of flights away from Diamond status (for example, Delta seems to offering some crazy cheap flights on PVG-LAX route).
Do airlines care/like it if you do mileage runs? Last time I booked with Delta and had to call in to confirm my ticket (credit card issue), the rep on the phone didn't seem to believe the price I had and didn't seem too happy about it either for some reason (same day turnaround flight)