If I want to send a seed to someone. How would you do it securely? Is it maybe even possible through the tangle? For example I have a seed with 50Miota and I want to give it away to a friend who lives 200km away. How would you do it? And also in the machine economy it could be necessary that one person or a machine tells another machine its new seed. Maybe because the owner of the company has changed.
Never send your seed over the network, just explain to your friend how to generate it's own seed securely offline. Ask him one address and transfer the iotas.
Securing transfer is one of the main purpose of the iota network. It would be a very bad signal (from an educational perspective) to send him a seed over the internet (or even by any other way).
The Problem with sending a seed using encrypted messaging over the Internet is that you can never know if someone is remotely viewing what you are reading on your computer after the message has been decrypted, or if your device is infected with a key logger that reports your keystrokes over the Internet or buy some side channel such as a flashing LED.
It was made to address the possibility that the components used to make our devices have been compromised before we have even purchased them and yet still we need to use our devices to write send and read private messages securely.
ben75 has the best answer but still there may be times when you must send a seed such as when you are providing for a child's future with IOTA and neither the child nor the parents have any idea yet what IOTA is. Paper may be your best bet in that case because there is more chance that the recipients will loose the seed simply because they do not understand the encryption process.
This video shows that sharing private keys (not seeds) is required to facilitate multi-signature transactions. In that case I would recommend GPG encrypted messaging where the private key is not decrypted for use until it is safely behind an airgap where remote viewing is not possible without extreme efforts by highly sophisticated criminals or by the most well equipped and determined government agencies.
Ideally you would want to send it to them in a purely untraceable way. A few options:
1) Paper. Do it in real life on a piece of paper.
2) End to end encrypted messaging. Use a secure messenger, and burn the messages later.