[EGreg]

What are some good tools to measure the kind of stuff they report?

Demographics and invitations Whose invitations are more accepted And so forth

[papercruncher]

We are not using anything fancy, it's just Google Analytics, redis and postgres. If we send anything out to the world (email, link to partners, open graph action) we tag it either with a google analytics campaign or a unique identifier so we can trace it back to our database. Every 12 hours, using a bunch of SQL commands + API calls we get a report in the mail.