Eric Schmidt's aspects of e-mail not in Twitter

Question

In Google CEO Eric Schmidt's comments about twitter he highlights some aspects of the e-mail system that twitter lacks.

The aspects of e-mail he mentions are:

• storage
• revocation
• identity

Could anyone explain these aspects of the traditional e-mail system? I'm interested in creating a twitter-like system and would like to better understand existing communication protocols and their abilities/characteristics.

Answer 1

Since after 6 hrs. no one has answered this I'll give it a try.

• storage

Well you can't store your tweets the same way you can store your e-mail, do you?

• revocation

Mmhh, perhaps because in an e-mail you can take back some comment or discuss back and forward about some topic keeping the thread in one place.

• identity

  The email identifies you as a user in a domain ( user@domain ) hence creates an on line identity. Twitter does not ( at least yet )

Twitter didn't include these kind of features because its nature was well, not being an e-mail susbtitute.

web-forums ( like this ) also evolved from the e-mail system, where all the questions/answers use the e-mail as communication channel.