According to http://lsvp.wordpress.com/2008/09/02/facebook-selling-digita... facebook is selling digital gifts at a $35m run rate. A friend at fb tells me this number is significantly inflated though.
You could send three different kinds of flowers to someone -- a cheap one ($1), a medium priced one ($3), or an expensive one ($10. Yes, $10 for a stupid little flower icon.)
People bought flowers by the hundreds of thousands; they became one of the biggest drivers of site revenue. Moreover, and this is interesting, James said that when someone sent a flower to a person, they were considerably more likely to get a response when sending a message.