The idea is to make it as seamless as possible, email your friend, your friend clicks the link, bam! the money is in their account. Better still if there is no need for a client install.
The closest seems to be Youtipit (swinewine, I did have a look at your website) with the Facebook linkage, but how do you get the bitcoins to them? Are they virtually in the Youtipit account?
The other possibility is instawallet (mineority, I also did have a look at your website). Perhaps you can make a button on your website where a single click: (1) creates a new wallet, (2) populates it with some of your bitcoins, and (3) sends your friend an email with the link and a personal message. If the user needs to go to his bitcoin client to fund it, then perhaps the button (1) goes to a page where you can compose the email, (2) creates the empty wallet, (3) queues the wallet ready to go out when it is funded. Then when the user funds it, your process automatically sends out the email. Maybe the email can include a link to the trade directory, besides allowing the composition of a personal message.
kwukduck -- individuals will have to fund it, in the spirit of P2P. As a miner (or investor) sitting on a stash of BTC, it might be worthwhile to donate some to friends to stimulate the economy. After all as a miner you didn't actually buy your BTC, and giving it away might cause the BTC to go up in value.