also:

* even within the same alliance having more than one program activ can sometimes help to acquire much more miles without having to fly more. My own best examples from the past are StarAlliance promotions fly NNN carriers in a specific time window earn NNN bonus miles: I just did with one rtw ticket fly two segments with each carrier and earned the overall maximum bonus twice (I did credit one segment to Mileage Plus and the other one to miles&more) and earned twice 100'000 bonus miles then. In May 2007 Star is 10 years old ... (I am hoping ...).
* miles&more status only expires every second year (and has to be renewed only every second calendar year too and I get some perks like upgrade vouchers only every second year), so every other calendar year I post my status miles with UA MileagePlus and get every other year 1K-status with them (and SWU upgrades etc).