Steam is a "Service"?

It does, you just open your friends list and it shows you what games are playable there, and whether you can join them.
The support for this has to be coded into the game, though.

Because I don’t want to bother people who are really busy?

Okay, so I play fighting games. Clearly most people here don’t. But if someone is in Training Mode, they’re much more likely to accept an invite to a game than they are if they’re already playing with people.

I have literally never seen an indicator of ‘joinable’ or anything on my friends list. o.o

A game it works well on that I play is Saints Row 4. If someone is playing that, I get a thing on my friends list telling me they’re playing it, and an option to Join. Obviously, they get the option in-game.

It’s not used in many games, as far as I can tell. But that’s the devs not making use of what’s available.

Very close. The only publisher that comes to mind that can successfully operate without Steam is Blizzard, and they’re a behemoth. For everyone else, yeah, Steam is a sine qua non.

Well, but typically people have founded a very successful internet service sell it for a fortune to the like of Microsoft or Google, and it goes south from there. I’m sure they are eyeing it. The most successful game provider on the web, and a social media too. They will want it, they will have it. And they will mess everything up.

If it’s an LLC, there are shareholders. A private company can be held by shareholders and the shares can be sold.
As for the second half, I say that the current shareholders won’t be there indefinitely, you say that unless they sell/retire/die, they’ll be running things for the foreseeable future. Those two statements do not intersect.

We must trust in St. Gabe, hallowed be his name.

Steam lists out all of it’s game services and publishing services on it’s own webpage. You might not personally use any of them but they are undeniably services.

From a developer’s perspective, if you’re a store, then I ship you a binary that’s the same as every other binary and you deliver it to the user. If you provide a service, then I need to manually change my game code to integrate with that service and I have a binary that’s customized to depend on the service API.

Electronic Arts seems to be staving off bankruptcy despite all their new titles the past few years being Origin only. Ubisoft releases on Steam but I have no issues with the Uplay service. The only time I really miss Steam is titles that don’t use any major service and thus languish in my “purchased games” list on Amazon or Gamersgate.

Yes and no.

It depends on how the owners want to define it.

E.g. Liz and her law partner have their firm set up as an LLC. Each holds a 50% stake in the company. They are treating it as “shares” in the sense that they own percentages of the company. But it’s not as if there’s a specific quantifiable number of something outside of a percentage of their company’s net worth (and potential net worth) that either could sell off as “shares”.

And, the fact that they are a law firm means that only another barred attorney could even buy into part of that firm’s value.

So referring it to as “shares” is really a matter of semantics.