Why does tor require administrative access to start, if it binds to a port higher than 1024?
On both linux and windows, administrative access is required.
Tor routes all network traffic through what is similar to a VPN (by creating a network route).
With other solutions like the built-in Windows VPN client, either a service running as SYSTEM or the operating system itself will make the routing changes on your behalf without making you authenticate as an administrator.
Since Tor doesn't use such a service and the operating system doesn't make special allowances for the Tor program, Tor needs to make these changes itself and therefore needs administrative rights.
I mention Windows because what's what I'm most familiar with, but a similar argument applies for Linux, I imagine.
Tor does not require administrative access to start. I have it running on my development machine as a limited (non-administrator) user.
I can start it with or without Vidalia, binding to ports larger than 1024, and everything works flawlessly.
I am running on Windows 7.