I guess it also depends on your flying pattern. Being based in AMS, it's relatively easy to get top tier status in all three alliances. BA Gold is just 800 tier points (although I usually fly double that in a year), LH SEN is 100,000 miles and FL Platinum is 75,000 (I think). LH SEN is easy to attain if you do some hopping around in Europe in business class, as you get 2,500 miles for each sector. So a day trip to, say, VRN from AMS is four flights at 2,500, or 10% of the miles necessary for getting SEN. Throw in the occasional long-haul on *A in business (at double the miles), and SEN is within easy reach. FB Platinum is mostly the result of flying AMS-NYC, as SkyTeam is the only alliance to serve that route directly. Under the new FB rules you accrue only 150% when flying in C long-haul, so it's gotten a bit harder. Still, I already have almost 25,000 miles to carry over into 06 towards status, and flying AMS-LON in C also gives me 1,500 per sector. SQ PPS is essentially two business trips to Asia for me: 20 sectors for flying Europe-Singapore, plus some hopping around in Asia and you're there. The double dipping feature also helps with the LH SEN status.

If you're only flying US domestic, or don't get to fly in business or first, then getting top tier status in all three alliances would be a lot harder. I'm still trying to maintain the status in all three as it's not that hard to do given my flying pattern, and I figure I might get some marginal benefits from it. As number_6 mentioned, airlines may be looking at other things than purely status for deciding how to treat their customers. Just do a search for CCV on the BA board. SQ keeps track of the number of years you've been QPP, TPP or LPP (PPS, Solitaire, Lifetime Solitaire) and that determines the pecking order. LH now has the HON level to separate the wheat from the chaff. With KL, the level of rudeness is probably totally random.