It's not necessarily the category of the item (C/U/R), it's the random packaging.
Action figures are collectible in the strictest sense of the word, but they aren't randomly packaged (unless you consider WotC minis to be action figures). You know what figure you are buying when you get the package.
If I collect Star Wars figures (again, exlcuding the WotC minis), I don't wind up with 15-20 "common" stormtroopers trying to luck into a "rare" Boba Fett figure I want. If I want Boba Fett, I buy Boba Fett. If I want 15 stormtroopers, I but 15. If I only want only one stormtrooper, I buy one.
Even without random minis or power cards, D&D is collectible. We all of us here have a "collection" of D&D books and game accessories. Even if we merely purchase the ones we like and pass on those we don't, it's still a collection. Moreso, I think a lot of gamers often purchase a book that may not have much utility for their game, but will add to the collection or make sure they have a complete set.
I DO appreaciate what WotC is trying to do by introducing a product that the local game shop can use to ensure hosting a game is profitable while ensuring that a player who buys one pack isn't at a mechanical disadvantage over one who buys many.
I guess I have no strong feeling one way or another. I'm not interested in the cards as they are being marketed so far, but , as others havem entioned, I can think of some houserule uses to reward good roleplaying. I also don't begrudge anyone else using them in their game.
It's an interesting discussion, either way.