In planning a rtw trip through oneworld, i'll be visiting most of the world's major cities.
I'll be going through places anywhere from Los Angeles, New York, London, Dubai, Cairo, Johannesburg, Sydney, Great Barrier Reef, Seoul, Bangkok, Singapore, Bali, Hong Kong, and many other exciting places, most of them being major cities. My purpose of a rtw is to travel and experience new things, but gaining status is important as well. While i'm already doing this with my rtw ticket, i would also like to do it will a couple of hotels as well. It would be nice to be upgraded once in a while. I was wondering when visiting a large amount of major cities, i am wondering how many hotel loyalty programs one should be in while on this massive trip. Originally, i thought three would give me flexibility as there would be more locations to choose from. As well, some hotel chains are more expensive in certain places (ie. Starwood hotels in Europe are more expensive then in USA). Three would give me more choices, however, it would be harder for me to gain elite status with their loyalty programs meaning less benefits.
1) How many hotel programs should i use while on my rtw?
2) Which ones should i go for? (considering frequency of upgrades, lounge usage, how easy it is to gain elite status).

If you really want to gain status within the hotel programs, then I would say just go for just one or two. It depends a bit on how many hotel nights you will get during your trip, but I think that you at most will only get enough stays/nights to get top status in one program.

Choose a hotel chain where you are likely to stay during later trips as well, otherwise your status is pointless. The relative merits of the different programs are discussed quote a bit in the Hotel forums, so check there to find out which is best suited for your needs.