"Did You Mean" in Gmail

Google has added a "Did You Mean" in Gmail labs. Basically, the feature tries to determine if you are about to send your email to the wrong person. What makes it particularly interesting is that it may be able to tell despite the contact having the same name. They are referring to it as "Got the wrong Bob?" feature.

http://gmailblog.blogspot.com/2009/10/new-in-labs-got-wrong-bob.html

"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.

While we were at it, we also changed the name of "Suggest more recipients" to "Don't forget Bob" — the two related Labs features just kind of went together better this way.

If you want to test "Got the wrong Bob?" out, try faking a mistake like this:
1) Think of three people you often email together.
2) Compose a message to two of them.
3) Start typing the third member of the group (for help you can use one of the people we suggest in "Don't forget Bob"), but then auto-complete on the wrong name."