Google GMail labs have introduced "Goth The Wrong Bob?" feature that helps to eliminate costly mistakes of sending email to the wrong person, when you have multiple Bobs or Smiths in your contact list. Once enabled the feature will learn from your frequent emails people whom you group together. And if a unfamilier Bob get into the list it will question you if this is the real Bob you meant to send the email, like below.
If you normally email Bob Smith together with Tim and Angela, but this time you added Bob Jones instead, we'll warn you that it might be a mistake. Note that this only works if you're emailing more than two people at once.New in Labs: Got the wrong Bob?