This is a compelling idea; it makes email more efficient in the same way Twitter makes blogs more efficient. There is power in concision. However it would make

This is a compelling idea; it makes email more efficient in the same way Twitter makes blogs more efficient. There is power in concision. However it would make a lot more sense to build it on top of Twitter DMs than on top of Gmail. Your Twitter friends expect curt messages, whereas many regular email correspondents will find subject-line-only email rude.