When you visit Steam download page from a web browser running on a Linux based OS, you are pointed to Linux version of Steam's website with a link to Steam for Linux beta shown above.
However, Valve is now showing the same page to Windows users as well, encouraging them to download Ubuntu and try out Steam for Linux beta. We all know about Gabe Newell's hatred of Windows 8 so this shouldn't be a surprising move.
Go to http://store.steampowered.com/ and click on Install Steam to see the promotion in action.
Via: Ubuntu Vibes