"Got the wrong Bob?" is a new Labs feature aimed at sparing you this kind of embarrassment. Turn it on from the Labs tab under Gmail Settings, and based on the groups of people you email most often, Gmail will try to identify when you've accidentally included the wrong person — before it's too late.

Finally there is a new feature to help Gmail user (f.e. employees from a bank) to send stuff (trustful information like customer details) to the wrong person...

Check also the comment a few weeks ago.

A US bank is suing Google for the identity of a Gmail user after a bank employee accidentally sent the user a file that included the names, addresses, tax IDs, and loan info for more than 1,300 of the bank’s customers. (...)

After a failed attempt to recall the email, the employee sent a second note to that wrong address, requesting that the confidential email be deleted before it was opened.

That's funny, a stupid bank employee makes a major mistakes and next the bank sues Google because they respect the privacy of their users.

I like that Google behaves like that, the bank is responsible for their mistake.

An add-on I use in firefox, amongst loads of other users; Gmail Manager - https://addons.mozilla.org/en-US/firefox/addon/1320

It has recently stopped working,

if you're using the firefox addon "Gmail manager", you might have noticed that authentication is not working as normal. The inbox check has stopped working too.