The rarity of cards has never stopped anyone from net-decking. It has just forced them to choose between spending money and losing. Typically, when you build a magic deck, you don't look at what cards you have, but what cards are legal in the current format. When you're done, you go out and get the cards that you are missing. Theoretically, if every player had access to every card in the game, they would probably still play the exact same decks.

In online games, casual players are mixed in with more serious players, so you play against tournament-style decks even in casual play. This will put pressure on the casual player to get the money rares. From my perspective, having all of the cards available to everyone will not change the decks people are playing at all. It will only make the game cheaper for the players.