By: Hillel Fuld

We are living in very interesting times. With Facebook’s growing dominance and Twitter’s expanding user base, hundreds of millions of people share every last detail about themselves openly on the Web. This of course changes everything. Going to a meeting is not what it used to be. The question “how will I recognize you in the crowd?” is no longer relevant. Before I meet anyone, I generally look them up on Facebook or Twitter to see who the person is and learn a little bit about them. Rapportive is an add on for Gmail that brings that information to your inbox.

The concept could not be simpler. Gmail is a wildly popular Web-based email client where people are spending hours of their time throughout the day, and Rapportive integrates flawlessly into Gmail’s interface. So how does it work? When you receive an email, the sidebar, where you would usually see Google’s advertising, is now occupied by the sender’s various social network profiles.

Many people would claim that eliminating Google’s only source of income from their free email client is nor an ethical not intelligent thing to do if you are a small startup, but putting that debate aside, Rapportive brings your Gmailing experience to a whole new level.

The add on is available for Chrome, Firefox, and Safari, and like other extensions, takes less than two minutes to install. Once installed, upon clicking on an email, you will see the sender’s picture, email address, current professional position, Twitter account, latest tweets, Facebook, Linkedin, and MySpace accounts. In addition, there is a field to add a note about the person, which will be displayed every time you get an email from them.

I could think of so many scenarios in which Rapportive would be beneficial, and it has provided me with added value on countless occasions. One feature I had not noticed until recently is that you can actually see how many times people have viewed your Rapportive profile and you can edit or remove the parts you do not like.

Some people have expressed concerns over privacy issues, which brings us back to the famous debate of online privacy. Rapportive takes all its data from sources that are already available to the public, so if you do not want that information displayed to your email contacts, perhaps you should think twice about tweeting it or posting it on Facebook. Just a thought. To me, this is a non issue.

If everything you have read so far about Rapportive has not convinced you to install the add on, maybe this will. The company has already raised over $1 million from leading people in the industry including Jason Calacanis, Gary Vaynerchuk, and the actual developer and creator of Gmail, Paul Buchheit.

I would strongly recommend installing Rapportive. If not for the ability to find out more about the person sending you an email, Rapportive also solves another well known problem of finding interesting and relevant people to follow or connect with on the various social platforms.

The company has an active presence on Twitter and when I voiced a concern about the add on not always finding information about people, they responded to me immediately saying they are always looking for ways to improve their databases.

While Gmail, like many Google products is simplistic in its user interface, Rapportive is a necessary addition and one that enhances the overall experience. In fact, with all of Google’s attempts at social integration into their various Web services, perhaps someone over there should throw out the idea of acquiring Rapportive since they seem to have perfected the concept of bringing social media into your inbox.

Watch the video below in which the developers of Rapportive talk about their product, its launch, and growing popularity. If you have tried Rapportive or if you have an opinion on it, please share it with us in the comments or reach out to me on Twitter here.