With the latest firmware of the Zune, Microsoft has done away with the restriction of 3 days to listen to that song that your Zune friend sent to you, but the 3 play restriction is still there.
A workaround has been found so that you can wirelessly share songs with your friends without your friend having to deal with the 3 plays restriction.
All you have to do is change the genre of a song to “Podcast” and than add the song to your Zune library.
The song will be listed under Podcasts but when you send the song to your friend, and he/she syncs the song back to their computer all they have to do is change the genre back to whatever they want it to be and re-add the song to their Zune library.
There you have it all, thanks to zunescene.com for finding the workaround, it is fairly simple but pretty cool.