A few examples of why I'm thinking this... budget computer systems, with Linux as their default OS, appearing on major retailer websites (and in some brick-n-mortar stores) for purchase.

Yes, Dell, HP, and IBM/Lenovo have offered Linux PC options prior to (and during) 2007, but they were never competitively priced or were easy to find on their websites to purchase in the first place. But now (and during the latter part of last year), you could find the Everex gPC on Wal-mart's website after just a couple clicks of surfing around (Electronics -> Computers -> Desktops w/o Monitors).

Not long after that, ASUS comes along and launches their new ultra-mobile PC, the EeePC, which is kicking serious butt in the computer market. In Canada, the EeePC is being sold by major retailer The Source, not to mention several specialty shops across the country.

Soon, Everex is going to be selling their own ultra-mobile PC, the Cloudbook, to try to take advantage of the market ASUS has opened up (sold through Wal-mart as well); followed closely by Acer and Gigabyte (I've never heard of them before) who are going to selling their own UMPCs.

To compete with Walmart's gPC offering, it now appears that Sears is selling another $200 desktop PC, running Freespire.

So, just to recap the recent activity of Linux based PCs in the main-stream market:

WalMart selling gOS Linux desktop PCs,
The Source selling ASUS EeePCs,
Sears selling Freespire desktop PCs.

And then there's the upcoming release of Everex's Cloudbook, and the two UMPCs from Acer and Gigabyte... as well second generation EeePCs coming this Spring from ASUS.

When compared to what's been happening in the Linux world previously, 2008 really seems to be Linux's explosion onto the global market. Is it the "year of Linux"? It's difficult to say, as I don't know what 2009 will bring. But it certainly is looking good.