Just downloaded it. I like the UI and the concept. Difficulty is with no friends on it I'm not able to get the full effect. I don't want to spam my friends so... how about having some public flocks?
A web presence of these public events could rank you up in google - say I tell flockers I'm going to be at the MongoDB group - and anyone who wants to come can join. If some one googled mongodb group in a city - Flock could be high on the ranking.
Just my random thoughts / ideas.