The CPMs on event related things might be high enough to just rely on ads.
http://mixergy.com/evite-harry-lin/
"effective CPM, when I left the company, we got, we’d driven it up, the effective CPM was just under ten dollars. And on certain pages, certain classes of pages, we enjoyed a one hundred dollar CPM, on all those ads"
http://mixergy.com/evite-harry-lin/ "effective CPM, when I left the company, we got, we’d driven it up, the effective CPM was just under ten dollars. And on certain pages, certain classes of pages, we enjoyed a one hundred dollar CPM, on all those ads"