The upcomming standards like 802.1x (security) and 802.11i (security wlan) will make access points and terminals secure. Today you can secure it with IPsec, but it is not as easy. One problem with IPsec is not securing on MAC (Level 2) layer, but on IP (Level 3). Having the security on level 2 will make it possible to secure a switch (bridge) acting as an access point.
Side note: Using upcomming standard 802.11e (QoS) can give away anonymous access and limit it to a max allowed bandwidth.

That's nonsense. VNC does not allow you to "setup a Windows box and have 50 Linux desktops connect to it"--VNC doesn't magically transform a single user Windows machine into a multiuser machine. I wish it did, but XP is such a primitive system that that's not easily possible. As far as Windows is concerned, VNC gives you the ability to remotely control a machine into which you are logged in, no more.

In any case, what matters is not whether VNC lets you do this but that Microsoft tries to impose such restrictions. It's just another indication of how much they are trying to milk and control their customers. Any rational buyer should run from that kind of company, and this should be added to the long list of anticompetitive practices to be investigated.