Change is in the wind.
As far as I know, when Valve released Half-Life 2 via Steam, they became the first developer/publisher to offer a top-tier AAA title using online distribution, right from the release date.
Hopefully, this will become the first of many. It doesn't look like there's a tidal wave of titles just waiting to be distributed online right now, but I'm hopeful. The toe is well and truly in the water - at the moment, the online purchase-and-distribution outfits seem to be ending up with what I'd call the "rental market" games - games that are approaching the end of their shelf life, those that the developer or publisher has essentially nothing to lose by distributing online.
I don't know if the market is big enough to be called "fragmented" at the moment, but it currently breaks down to Valve's Steam and Everything Else. Of Everything Else, the most visible provider of recognizable commercial titles seems to be Gamespy/IGN's Direct2Drive.
I was thinking about this because I was wondering why World of Warcraft isn't available online. If ever there was a candidate for online distribution, you'd think it'd be an MMORPG - there's no way you can play without having an account. Let the world copy the base CD image again, and again, and again, but charge them the "setup fee" when they first sign up to play. Everyone pays, everyone wins.
With traditional (eg, non-multiplayer games with no central authentication server) titles, the games end up wrapped in lockboxes, waiting to be unlocked by an activation code. The same thing applies here (really simplified) - if someone copies a game, it's not usable without the appropriate unlock code. I don't know how this compares to the utterly annoying CD-ROM-in-the-drive requirement that most games use for copy protection, but if it means I don't have to constantly keep the discs for the games I'm using near the computer, I'm all for it.
The market may not be ready for buy-online-only games (heck, it might be - are you?), but when it is, what do you think will happen? Will we see Indie co-ops offering games from their own co-operative online store? Publishers transitioning from traditional publishing to online distribution, or farming the work out to third parties? Price drops across the board from reduced manufacturing and distribution costs? Ancient and rare titles offered for download once again, just in case someone wants to buy Fallout, Sam'n'Max, Descent II, EF2000, Edge of Chaos, or Wing Commander 3/4 (again in many cases, due to lost CDs)?
A plea to the publishers - c'mon people! My credit card is ready. I don't want to have to drive to the shops to buy stuff. Please give me what I want, online (and what I want is everything)!