It seems pretty commonplace now for signups to go something like this:<p>Step 1 Sign up and verify you are not a robot --><p>Step 2 Connect and invite friends through an email import program --><p>Step 3 splash page or call to action to start using the site.<p>It seems like if the big guys are doing this, then there is likely a lot of data to suggest it works. Additionally, the book - the Viral Loop -- seems to suggest this is a critical piece to viral growth. The question then becomes, is there a wrong time to implement this functionality in a site's development? i.e., is this something you should launch once you have a fairly significant userbase?<p>Any experience experimenting w/this?