Just generated this graph:

http://imgur.com/iqnaGem

We had 38 signups yesterday, grew ~44% in the last 30 days.

EDIT, mathfail: grew 79% in the last 30 days.

Cool. Is your transaction volume growing at the same rate?

Here's a graph of the transaction volume:

http://imgur.com/ScNqb4I

The big spike in the beginning was before we implemented fraud checks (eg, users directing botnets at the shortlinks).

Since then, the transaction volume has been growing at a similar rate, at 70% growth in the past 30 days (compared to 79% user growth).