His concern isn't much to worry about. He's afraid that if Steam has no competition and "wins", Valve will stop innovation in the Digital Distribution world. The thing is that there's alot of up and coming DD services that are looking to compete, such as Impulse, GFW (crap), GOG, and Blizzard's Battle.net if they fully go with the plan to make a Steam-like service.
As for the indies comment, Steam is just one DD service where they can sell their games, so if they don't like it then don't come to Steam. There's hundreds of DD stores where they can sell their games. Steam has a userbase of over 20 millions, and Steam gives a much bigger exposure than the other DD stores.
Garry's Mod, a game/mod made by an indie guy, sold over 300k units on Steam in just 2 years. Valve got 50% of the money made, but the guy still became a millionaire. The Garry's Mod is a unique case though, because it's a game that works only on Source games, which is why Valve got 50% of the money. For the other devs, Valve probably gets around 30-40%







