In the past, Google has introduced Gmail Labs additions like Mail Googles (to prevent those potential drunk-dial by e-mail moments) and "Undo Send" which let you cancel sent messages if you act fast enough. Today Gmail Labs is introducing a new feature for the user with lots of contacts with similar names, "Got the wrong Bob."
"Got the wrong Bob?" is for those times you send a group mail that includes the wrong person. If you have multiple friends named "Adam" or "Dan" or "Chris" for instance, you might sometimes select or send the e-mail to the wrong person.
"Got the wrong Bob?" looks at the people you frequently e-mail and points out irregularities -- like if you have an e-mail that is normally sent to a group including Adam H. instead including Adam O.
It's a pretty neat idea, but keep in mind it only works for e-mails sent to more than one person. It still won't stop you from sending a personal message to the wrong Erik.