Don't know if this has been mentioned but with regard to the stickers as a never-ending collection thing...
In SSB:M, after receiving the Pikmin trophy, I wanted EVERY freaking Nintendo game to unlock a new trophy. Then trophies would prove how much of a Nintendo fan I am (except that my Blockbuster never did carry Chibi-Robo and I never got around to Odama...). The problem with that is that SSB:M would have to be set up in at least one of three ways:
a) the new trophy data would have to exist in the original game, with five years worth of games planned out, which would require too much foresight.
b) OR, the new trophy data would have to be on some online database, but the GameCube's online capabilities were never truly tapped.
c) OR, the new trophy data would have to be included in the save files of every Nintendo game made, with SSB:M already programmed to scan all the saves on the Memory Cards and be ready to extract data from them - and 3D models probably take up quite a bit of space which would balloon save files which would not be cool for non-SSB:M owners.
However, stickers are simple 2D images, which would take next to no time to download, or add minimal extra space to saved games, which makes b) and c) above now feasible. I would prefer b) so that we could get stickers for Wii games that already exist that likely do not have sticker data.
UNLIMITED COLLECTING! Okay, maybe not unlimited, but quite expandable!
While I prefer trophies to stickers, you could probably collect a lot more stickers especially with the possibilities above, you can do more stuff with them, and multiple ones would serve an actual purpose.