In case you have not noticed, older macs that can run lion do not support air drop. There is a way around this. 1.) Open Terminal and type defaults write "com.apple.NetworkBrowser BrowseAllInterfaces 1" without the quotes and press enter. 2.) type killall Finder. You will have to do this on all of the machines that you want to connect to. Now when you look on the side bar of the finder you will see Airdrop and you can now use it to connect to other macs.