How do programs like PANDO work?

Answer 1

That's an interesting question. :)
It's a combination of regular download and P2P (like Kaaza and bittorrent).
First you upload the file to their server. Then, the person(s) you indicate will receive an e-mail with a .pando attachment. Finally, he (or she) will open the file and start downloading. At first, the file will be trasnfered from your machine and pando's server. Then, as time passes, the other recipients will share the pieces that they already got, making the transfer faster. After 14 dias, the file is deleted from pando's servers and the sharing proceed as a regular P2P.