Glenn Fleishman explains a tiny tweak you can make in Lion that enables AirDrop peer-to-peer file exchange to work over local area Ethernet and wireless networks. This enables AirDrop for older Macs that lack the right Wi-Fi chips to work with AirDrop out of the box, and it also adds wired LAN access for even those Macs that do have supported Wi-Fi chips. follow link
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Enable AirDrop for All Macs with Lion
Check out the Take Control ebooks that expand on the topic in this article:
Read real-world advice from Wi-Fi wizard Glenn Fleishman on setting up a wireless network using Apple's 802.11n and 802.11ac base stations. Learn to maximize performance, extend range, connect multiple base stations, handle complex configs, share USB disks and printers, and more.