If you have a need to enable or disable Screen Sharing from a terminal in OS X the commands are very simple. I’ve used these commands in 10.6 (Snow Leopard).
Enable
sudo touch /etc/ScreenSharing.launchd
Disable
sudo rm /etc/ScreenSharing.launchd
Source: rentzsch.tumblr.com | Starting VNC remotely via kickstart
Updated 06/07/2012: It seems that the process for doing this has changed in OS X Lion based on a post in Ryan’s Tech Notes. I used these commands and they worked as described.
Enable
sudo /System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/kickstart -activate -configure -access -on -clientopts -setvnclegacy -vnclegacy yes -clientopts -setvncpw -vncpw mypasswd -restart -agent -privs -all
Disable
sudo /System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/kickstart -deactivate -configure -access -off
Press Any Key 
I have this problem actually but I am on Ventura. Regardless I tried the above commands and they did not work. I have a hacker though, who got into my Wi-Fi network and from there I think got ahold of my Wi-Fi network traffic and then got my passwords. Not sure. Either way I really need this plz, it shows it’s sharing but doesn’t. I know it is. He is also using a local network he set up on my computer on the Ethernet bridge. So yeah. It gets better and better tho but that’s where I’m at. Plz help