Numbers of registrations is a vanity metric. How many used the core product? How many retained? How many converted to paying? How many told their friends?
To answer your questions
"How many converted to paying" --about 3% converted to paying, which is slightly lower then our normal traffic (4-5%). A lot of the "non-converts" were part of the foreign traffic we eventually moved to a wait-list until we can enter those markets with a more strategic plan
"How many retained" --This is an interesting question. Most people used the product, 3% paid. Remember, our product is meant to be free, so many people do some upfront work and then just check their email progress reports to make sure everything is still OK. Our email open rates have never dropped below 60%, so many people are retained in the sense that they check those emails. We'll have people who signed up during that surge that will pay us for the first time today based off one of those emails
"How many told their friends"
About 75% of users tell somebody else. This is based on a user survey. The problem is, almost all of them tell people in person. They tell them over dinner, or at an event when someone mentions their Google results. We haven't figured out a way to capture that same rate through online vehicles.