They also let you do transfers. Which was in TFS if you bothered to read it. You can do this without sending account numbers (just use account suffixes) but what happens when your twitter account gets hacked and someone transfers all of your money from your checking suffix to your savings? Say hello to overdraft fees.
If your twitter account gets hacked you just call up the bank and disable the twitter feature till you get the problem fixed or a new account?
The universe is an island, surrounded by whatever it is that surrounds universes.