http://marketshare.hitslink.com/operating-system-market-share.aspx?qprid=10
4% vs 1%

True that, but as it happens PC gaming is further mired with MS than it has been for some time. GfWL et al are a bit to much for my liking.
Of course, PC Gaming = Steam Gaming annoys me just as much (MW2, DOW2, Empire:TW, Metro 2033, Batman AA... the list goes on).
Still, we shall see how much Mac stuff Valve/Steam can bring to the table. Might turn Mac users into gamers...

And gamers into mac users.

Honestly, percentage doesn't mean much without the real world numbers in terms of actual systems running each OS. There are currently about a billion desktop computers in use worldwide, so that 1% that Linux holds translates to roughly 10 million machines. That's actually a significant number of potential customers for game companies, but it is still absolutely nothing in comparison to the 950 million machines already running some form of Windows. Sure, there are people who would switch to Linux or some other OS if it weren't for the fact that commercial gaming is pretty much restricted to Windows, but not enough to make any kind of significant dent in that 95% market share that Windows currently holds, especially when nearly all new desktop PCs are sold with Windows pre-installed and most average consumers would never even consider changing that.
Yes, it would be nice to see developers supporting Linux, even if it means Steam comes to Linux, but the fact is, the Linux community is stuck in a "chicken and the egg" scenario right now: game companies won't market to Linux users because there aren't enough Linux users to make it worthwhile; there aren't enough Linux users to make it worthwhile because (in part) there are almost no big-name commercial games on Linux. We will never see something like Steam on Linux as long as this conundrum exists. Unfortunately, it probably won't be games that bring desktop users over to Linux, it will more likely be something business or productivity related. That's what made Windows so ubiquitous, the fact that it ran applications like Office. It was only after the general public became accustomed to Windows through its use in a business environment that we started seeing it in the home environment and it became a viable gaming platform. If and when that happens to Linux, then we might see the beginnings of gaming support; lets face it, Steam coming to Mac is really only a beginning itself. The vast majority of Steam's current game library do not have Mac versions that we know of yet, so the Steam client coming to Mac is a start, but it could be just a really small start.

gaming is thriving on linux, or does nobody else here have a smart phone?

I have 200 games on Steam, 30 on Gog. I am primarily interested in those.
Regarding the 4%-1% stat, that could be 95% - 4%, potentially.

The "new Shiny" is what keeps the economy going, for better or for worse.

How do you figure that, everyone running Windows spontaneously switches to Linux? Even ignoring the fact that that is something statistically so unlikely to happen as to be a virtual certainty, it doesn't really matter: imaginary potential means nothing to game companies looking for the biggest return on their investment, facts are all that matter. The fact is, only about 1% of the desktop PCs in the world are running some form of Linux right now and that does not translate to a significant enough customer base to warrant the additional investment of time and money into Linux game development.

Why all the Steam hate? And by the way, the first Jedi Knight DOES work on the computer. They just didn't get the CD music from LucasArts!

Steve Jobs is willing to tolerate a potential competitor to the App Store on his sacred operating system?
If publishers release more Mac-ready games, Jobs will obviously want control over digital distribution. Perhaps he will welcome Steam, initially, in order to spur development on the platform. Eventually, however, I suspect that Apple's relationship with Valve will sour.

A virtual certainty?
Go back to Math 101 please. You cannot POSSIBLY predict the effect Steam going to Linux with 100% guarenteed compatibility would have on the OS stats. If you could, you would likely have a job in marketing, and be far too busy to post such trivialities on sites like this.

I said ages ago that Valve would be bought out within a year from now by either EA or Apple. Maybe this means a "merger" with Apple?

I doubt Steve Jobs will try to interfere with Valve, because if they catch a whiff of that, they will high-tail it out of there. Also, Apple is still an infant when it comes to truly knowing the gaming market.

Well, not only did you miss the point, your argument kind of flies against your own prediction... but I won't belabor the obvious.
The point you missed was that because of how things currently are, there will never be a version of Steam on Linux and it will therefore never be a factor in influencing anyone to do anything Linux related. It comes back to the whole "chicken and the egg" thing I said before: the games won't come to Linux because the people aren't there, the people won't come to Linux because the game aren't there. However, even if by some minor miracle, Gabe Newell changes his stated opinions on Linux gaming tomorrow and puts out a version of Steam and all of Valve's games that work on Linux, it still wouldn't be enough to to create the kind of paradigm shift you are describing, where hundreds of millions of happy Windows users suddenly decide that because Valve has graced the Linux operating system with the presence of Steam and Half-Life that they must mark this joyous... nay, holy day... by abandoning the OS they have used for years in favor of a different one they most likely have never... even.... heard of.
Then again, in a world where Gabe Newell decides to support Linux, pretty much anything is possible... kind of like in comic books!

I hate Linux. Linux makes me want to throw bricks at computers, because they would be better off dead than running that damn OS. I've tried to get it to work for me, but it's too complicated. How does anyone expect people who sometimes find Windows too tough to even consider switching to a harder platform?

they want YOU to get smarter