Well i think there are more ways than the obvious ones to be a principal platinum card holder (or, entitled to?).

Loyalty upgrades, Credit guranteed against personal FDs, Spending/repayment patterns (High volume transactions met with prompt payments in full) are also some factors that could nett you a platinum card.

Sometimes i think banks "advertise" the "Eligible" annual salary just to give prestige/status to its card offering or rather its holders. (nothing wrong with that though)

Ok, probably i have generalized too much so i end here lol.

Anyway was driving to office today and noticed a huge sign board that said 8X points for petrol purchases from Amex (anyone have a list of stations? or at least does it include ESSO/Mobil?). Now that is just awesome. (Dont have Amex though, might consider one as my master and visa cards offer crap rewards).