yes, the more people that play the more worlds they wil need to fit everyone
There are 159 worlds including the 4 dutch worlds
Currently, it's 82 member worlds in all of RuneScape, whereas 5 is in other languages.
there is no world were you can get random events more than other worlds.
on the pvp/bounty worlds
about 35
runescape
In the Edgeville bank, on BH worlds.
Runescape (if you have java) habbo, smallworlds, webkinz, neopets, etc. some, not much. Please make your questiob a bit more specific. What kind of worlds?
You risk more items yourself, the more you risk the more you get. You get good drops if you are risking 25k or more on a pvp world. This means that you would lose it if you died, and it is not protected by the protect item prayer. There is a great guide on how to own in Pvp worlds here: http://www.gameolosophy.com/Games/Online/RuneScape/How-to-Own-in-Pvp-Worlds-in-F2p.538733
Take a look on the world selection.
world 57
runescape, but you have to be 13+