What are your thoughts on competitors to Steam?

There must be huge costs in running a platform like Steam and I assume that is the main factor, huge bandwith and hardware costs.

However it must be tempting to create your own Steam like service, it would be fun to code it but would obvioulsy depend on investment.

So why do you think Steam is so successful and there afre no real rivals?

Here's plenty of rivals, but steam got in first and carved out a huge chunk of market-share for themselves. Things like steam chat, gifting, trade, forums, etc connect their users, so that they don't want to switch to other services. They also offer a lot of services to devs, such as the obvious file hosting and (very fast, global) distribution, patching, public/private betas, branches, micropayment API, VOIP APIs, NAT punch-through with free proxy fallbacks, matchmaking, lobbies, etc... On top of that, they've (seemingly?) got the majority of digital PC consumers on the hook, making their store a place you really want to be available from.
All this makes for a very strong feedback loop, keeping it the dominant force.

EA, Ubisoft and the smaller 'indie' versions don't even have feature parity... Along with having less consumers visiting them. Some of the indie ones are much more user friendly, such as having no DRM, or letting you use them without an account, but are competing as niche operators, rather than actual mainstream competition.

Some of the indie ones are much more user friendly, such as having no DRM, or letting you use them without an account, but are competing as niche operators, rather than actual mainstream competition.

I wouldn't call it completely niche. Hard numbers are difficult to come by but for The Witcher 2 release it appears online sales were 80% Steam and 16% GoG [see 'Market share' on Wikipedia. While that is obviously a large majority for Steam I'm unwilling to discard one in six as a niche (the 'others' who split the remaining 4% would probably count as that...).

Trying to usurp Steam as an online distributor is probably a bit like trying to go up against WoW with an MMORPG that plays exactly like WoW. Unless you have some unique shtick the work, money and time required to even get to feature parity is simply too much. GoG has written 'no DRM' and 'fair pricing models' on its battle flag. That's unlikely to be enough to break the Steam dominance but seems to work well to carve out a small but steady share of the market.

The Witcher 2 numbers on GoG might be a bit inflated, given that CDProjeckt made The Witcher and GoG, so its a favorite among The Witcher players. I wouldn't expect those numbers with an unrelated game developer.

Possible, but the numbers of the independent Defender's Quest were similar.

For one thing, are there even enough PC games coming out to support very many major portals? This is a case where the "pie" is a fixed size, so jumping into the mix means you'll be fighting for a small slice of it in the best case scenario. I can't see a new portal bringing in new gamers that aren't buying games now. GoG may have done that to a point with no DRM, but what's left to add?

My guess for the biggest 'alternative' to Steam would be Big Fish Games. They focus on a specific type of game - casual, lasting 4-6 hours, that they can sell cheaply and profit: Hidden Object, Match-3, Time Management, Road Builders, etc... I would not be surprised at all to find out that HOPA's are currently the most profitable segment of PC gaming right now, though production costs from the major developers are rising: cinematic cutscenes, fully voiced, etc... The days when you could slap some clip art on a pile are pretty much done. Even Match-3 games have storylines with voiced characters now.

Possible, but the numbers of the independent Defender's Quest were similar.

Allthough a game like defender's quest is probably more likely to get a favorable reception with the gog.com users (who enjoy retro/classic games) than it would with the more diverse Steam userbase.

What happened to star breeze's platform? I presume it was bought up. Desura is good for super indie titles (with less emphasis on quality). But Steam has worked really hard for a Long time to be exactly what developers and consumers want it to be, I'd be amazed if anyone could top them in the next ten years.