So you give up your email credentials to LinkedIn and in exchange you get a little widget that tells you the name of the person who is emailing you, the company

So you give up your email credentials to LinkedIn and in exchange you get a little widget that tells you the name of the person who is emailing you, the company they work for, their position in the company, and some contact information? Isn't that's what the signature line is for? Seriously, don't people already setup their signature line to include all that information. It's a cool hack, however.