a16z’s @david__booth and @katiesquestions on what makes a Cosign different: you’re putting your own reputation behind someone else. David Booth: "LinkedIn is where you go to talk about yourself and the work you've done. Cosign is where your profile gets built out by the people who you have worked with." "A cosign is intended to be scarce and expensive. You can go on LinkedIn and connect with anyone you just met at the party. A cosign is public. You're attaching some of your reputation to…